Merge remote-tracking branch 'origin/master' into flakes

31 files changed, 974 insertions, 911 deletions

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 31f8f5862..66683e936 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1607,6 +1607,19 @@ bool EvalState::isDerivation(Value & v)
 }
 
 
+std::optional<string> EvalState::tryAttrsToString(const Pos & pos, Value & v,
+    PathSet & context, bool coerceMore, bool copyToStore)
+{
+    auto i = v.attrs->find(sToString);
+    if (i != v.attrs->end()) {
+        Value v1;
+        callFunction(*i->value, v, v1, pos);
+        return coerceToString(pos, v1, context, coerceMore, copyToStore);
+    }
+
+    return {};
+}
+
 string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
     bool coerceMore, bool copyToStore)
 {
@@ -1625,13 +1638,11 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
     }
 
     if (v.type == tAttrs) {
-        auto i = v.attrs->find(sToString);
-        if (i != v.attrs->end()) {
-            Value v1;
-            callFunction(*i->value, v, v1, pos);
-            return coerceToString(pos, v1, context, coerceMore, copyToStore);
+        auto maybeString = tryAttrsToString(pos, v, context, coerceMore, copyToStore);
+        if (maybeString) {
+            return *maybeString;
         }
-        i = v.attrs->find(sOutPath);
+        auto i = v.attrs->find(sOutPath);
         if (i == v.attrs->end()) throwTypeError("cannot coerce a set to a string, at %1%", pos);
         return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
     }
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 1cc3c8507..50c6f784e 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -9,6 +9,7 @@
 #include "function-trace.hh"
 
 #include <map>
+#include <optional>
 #include <unordered_map>
 
 
@@ -207,6 +208,9 @@ public:
        set with attribute `type = "derivation"'). */
     bool isDerivation(Value & v);
 
+    std::optional<string> tryAttrsToString(const Pos & pos, Value & v,
+        PathSet & context, bool coerceMore = false, bool copyToStore = true);
+
     /* String coercion.  Converts strings, paths and derivations to a
        string.  If `coerceMore' is set, also converts nulls, integers,
        booleans and lists to a string.  If `copyToStore' is set,
diff --git a/src/libexpr/primops/fetchGit.cc b/src/libexpr/primops/fetchGit.cc
index aea34b1dd..6f67e3d76 100644
--- a/src/libexpr/primops/fetchGit.cc
+++ b/src/libexpr/primops/fetchGit.cc
@@ -115,8 +115,7 @@ GitInfo exportGit(ref<Store> store, std::string uri,
 
         if (!clean) {
 
-            /* This is an unclean working tree. So copy all tracked
-               files. */
+            /* This is an unclean working tree. So copy all tracked files. */
 
             if (!evalSettings.allowDirty)
                 throw Error("Git tree '%s' is dirty", uri);
diff --git a/src/libexpr/value-to-json.cc b/src/libexpr/value-to-json.cc
index 72e413e44..5fe8570ad 100644
--- a/src/libexpr/value-to-json.cc
+++ b/src/libexpr/value-to-json.cc
@@ -40,7 +40,12 @@ void printValueAsJSON(EvalState & state, bool strict,
             break;
 
         case tAttrs: {
-            Bindings::iterator i = v.attrs->find(state.sOutPath);
+            auto maybeString = state.tryAttrsToString(noPos, v, context, false, false);
+            if (maybeString) {
+                out.write(*maybeString);
+                break;
+            }
+            auto i = v.attrs->find(state.sOutPath);
             if (i == v.attrs->end()) {
                 auto obj(out.object());
                 StringSet names;
diff --git a/src/libstore/binary-cache-store.cc b/src/libstore/binary-cache-store.cc
index 8e6f1f55d..7e3e5ff88 100644
--- a/src/libstore/binary-cache-store.cc
+++ b/src/libstore/binary-cache-store.cc
@@ -296,7 +296,7 @@ void BinaryCacheStore::narFromPath(const Path & storePath, Sink & sink)
 }
 
 void BinaryCacheStore::queryPathInfoUncached(const Path & storePath,
-    Callback<std::shared_ptr<ValidPathInfo>> callback) noexcept
+    Callback<std::shared_ptr<const ValidPathInfo>> callback) noexcept
 {
     auto uri = getUri();
     auto act = std::make_shared<Activity>(*logger, lvlTalkative, actQueryPathInfo,
diff --git a/src/libstore/binary-cache-store.hh b/src/libstore/binary-cache-store.hh
index c77292294..2d7cd1947 100644
--- a/src/libstore/binary-cache-store.hh
+++ b/src/libstore/binary-cache-store.hh
@@ -74,7 +74,7 @@ public:
     bool isValidPathUncached(const Path & path) override;
 
     void queryPathInfoUncached(const Path & path,
-        Callback<std::shared_ptr<ValidPathInfo>> callback) noexcept override;
+        Callback<std::shared_ptr<const ValidPathInfo>> callback) noexcept override;
 
     Path queryPathFromHashPart(const string & hashPart) override
     { unsupported("queryPathFromHashPart"); }
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 8e795e555..fe861e629 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -1875,6 +1875,21 @@ static void preloadNSS() {
     });
 }
 
+
+void linkOrCopy(const Path & from, const Path & to)
+{
+    if (link(from.c_str(), to.c_str()) == -1) {
+        /* Hard-linking fails if we exceed the maximum link count on a
+           file (e.g. 32000 of ext3), which is quite possible after a
+           'nix-store --optimise'. FIXME: actually, why don't we just
+           bind-mount in this case? */
+        if (errno != EMLINK)
+            throw SysError("linking '%s' to '%s'", to, from);
+        copyPath(from, to);
+    }
+}
+
+
 void DerivationGoal::startBuilder()
 {
     /* Right platform? */
@@ -2118,22 +2133,8 @@ void DerivationGoal::startBuilder()
                 throw SysError(format("getting attributes of path '%1%'") % i);
             if (S_ISDIR(st.st_mode))
                 dirsInChroot[i] = r;
-            else {
-                Path p = chrootRootDir + i;
-                debug("linking '%1%' to '%2%'", p, r);
-                if (link(r.c_str(), p.c_str()) == -1) {
-                    /* Hard-linking fails if we exceed the maximum
-                       link count on a file (e.g. 32000 of ext3),
-                       which is quite possible after a `nix-store
-                       --optimise'. */
-                    if (errno != EMLINK)
-                        throw SysError(format("linking '%1%' to '%2%'") % p % i);
-                    StringSink sink;
-                    dumpPath(r, sink);
-                    StringSource source(*sink.s);
-                    restorePath(p, source);
-                }
-            }
+            else
+                linkOrCopy(r, chrootRootDir + i);
         }
 
         /* If we're repairing, checking or rebuilding part of a
@@ -3264,8 +3265,7 @@ void DerivationGoal::registerOutputs()
             i.second.parseHashInfo(recursive, h);
 
             if (!recursive) {
-                /* The output path should be a regular file without
-                   execute permission. */
+                /* The output path should be a regular file without execute permission. */
                 if (!S_ISREG(st.st_mode) || (st.st_mode & S_IXUSR) != 0)
                     throw BuildError(
                         format("output path '%1%' should be a non-executable regular file") % path);
@@ -3343,8 +3343,7 @@ void DerivationGoal::registerOutputs()
                         % drvPath % path);
             }
 
-            /* Since we verified the build, it's now ultimately
-               trusted. */
+            /* Since we verified the build, it's now ultimately trusted. */
             if (!info.ultimate) {
                 info.ultimate = true;
                 worker.store.signPathInfo(info);
@@ -3354,8 +3353,7 @@ void DerivationGoal::registerOutputs()
             continue;
         }
 
-        /* For debugging, print out the referenced and unreferenced
-           paths. */
+        /* For debugging, print out the referenced and unreferenced paths. */
         for (auto & i : inputPaths) {
             PathSet::iterator j = references.find(i);
             if (j == references.end())
@@ -3413,8 +3411,7 @@ void DerivationGoal::registerOutputs()
             }
     }
 
-    /* If this is the first round of several, then move the output out
-       of the way. */
+    /* If this is the first round of several, then move the output out of the way. */
     if (nrRounds > 1 && curRound == 1 && curRound < nrRounds && keepPreviousRound) {
         for (auto & i : drv->outputs) {
             Path prev = i.second.path + checkSuffix;
@@ -4138,9 +4135,6 @@ void SubstitutionGoal::handleEOF(int fd)
 //////////////////////////////////////////////////////////////////////
 
 
-static bool working = false;
-
-
 Worker::Worker(LocalStore & store)
     : act(*logger, actRealise)
     , actDerivations(*logger, actBuilds)
@@ -4148,8 +4142,6 @@ Worker::Worker(LocalStore & store)
     , store(store)
 {
     /* Debugging: prevent recursive workers. */
-    if (working) abort();
-    working = true;
     nrLocalBuilds = 0;
     lastWokenUp = steady_time_point::min();
     permanentFailure = false;
@@ -4161,8 +4153,6 @@ Worker::Worker(LocalStore & store)
 
 Worker::~Worker()
 {
-    working = false;
-
     /* Explicitly get rid of all strong pointers now.  After this all
        goals that refer to this worker should be gone.  (Otherwise we
        are in trouble, since goals may call childTerminated() etc. in
diff --git a/src/libstore/daemon.cc b/src/libstore/daemon.cc
new file mode 100644
index 000000000..64147027b
--- /dev/null
+++ b/src/libstore/daemon.cc
@@ -0,0 +1,790 @@
+#include "daemon.hh"
+#include "monitor-fd.hh"
+#include "worker-protocol.hh"
+#include "store-api.hh"
+#include "local-store.hh"
+#include "finally.hh"
+#include "affinity.hh"
+#include "archive.hh"
+#include "derivations.hh"
+#include "args.hh"
+
+namespace nix::daemon {
+
+Sink & operator << (Sink & sink, const Logger::Fields & fields)
+{
+    sink << fields.size();
+    for (auto & f : fields) {
+        sink << f.type;
+        if (f.type == Logger::Field::tInt)
+            sink << f.i;
+        else if (f.type == Logger::Field::tString)
+            sink << f.s;
+        else abort();
+    }
+    return sink;
+}
+
+/* Logger that forwards log messages to the client, *if* we're in a
+   state where the protocol allows it (i.e., when canSendStderr is
+   true). */
+struct TunnelLogger : public Logger
+{
+    FdSink & to;
+
+    struct State
+    {
+        bool canSendStderr = false;
+        std::vector<std::string> pendingMsgs;
+    };
+
+    Sync<State> state_;
+
+    unsigned int clientVersion;
+
+    TunnelLogger(FdSink & to, unsigned int clientVersion)
+        : to(to), clientVersion(clientVersion) { }
+
+    void enqueueMsg(const std::string & s)
+    {
+        auto state(state_.lock());
+
+        if (state->canSendStderr) {
+            assert(state->pendingMsgs.empty());
+            try {
+                to(s);
+                to.flush();
+            } catch (...) {
+                /* Write failed; that means that the other side is
+                   gone. */
+                state->canSendStderr = false;
+                throw;
+            }
+        } else
+            state->pendingMsgs.push_back(s);
+    }
+
+    void log(Verbosity lvl, const FormatOrString & fs) override
+    {
+        if (lvl > verbosity) return;
+
+        StringSink buf;
+        buf << STDERR_NEXT << (fs.s + "\n");
+        enqueueMsg(*buf.s);
+    }
+
+    /* startWork() means that we're starting an operation for which we
+      want to send out stderr to the client. */
+    void startWork()
+    {
+        auto state(state_.lock());
+        state->canSendStderr = true;
+
+        for (auto & msg : state->pendingMsgs)
+            to(msg);
+
+        state->pendingMsgs.clear();
+
+        to.flush();
+    }
+
+    /* stopWork() means that we're done; stop sending stderr to the
+       client. */
+    void stopWork(bool success = true, const string & msg = "", unsigned int status = 0)
+    {
+        auto state(state_.lock());
+
+        state->canSendStderr = false;
+
+        if (success)
+            to << STDERR_LAST;
+        else {
+            to << STDERR_ERROR << msg;
+            if (status != 0) to << status;
+        }
+    }
+
+    void startActivity(ActivityId act, Verbosity lvl, ActivityType type,
+        const std::string & s, const Fields & fields, ActivityId parent) override
+    {
+        if (GET_PROTOCOL_MINOR(clientVersion) < 20) {
+            if (!s.empty())
+                log(lvl, s + "...");
+            return;
+        }
+
+        StringSink buf;
+        buf << STDERR_START_ACTIVITY << act << lvl << type << s << fields << parent;
+        enqueueMsg(*buf.s);
+    }
+
+    void stopActivity(ActivityId act) override
+    {
+        if (GET_PROTOCOL_MINOR(clientVersion) < 20) return;
+        StringSink buf;
+        buf << STDERR_STOP_ACTIVITY << act;
+        enqueueMsg(*buf.s);
+    }
+
+    void result(ActivityId act, ResultType type, const Fields & fields) override
+    {
+        if (GET_PROTOCOL_MINOR(clientVersion) < 20) return;
+        StringSink buf;
+        buf << STDERR_RESULT << act << type << fields;
+        enqueueMsg(*buf.s);
+    }
+};
+
+struct TunnelSink : Sink
+{
+    Sink & to;
+    TunnelSink(Sink & to) : to(to) { }
+    virtual void operator () (const unsigned char * data, size_t len)
+    {
+        to << STDERR_WRITE;
+        writeString(data, len, to);
+    }
+};
+
+struct TunnelSource : BufferedSource
+{
+    Source & from;
+    BufferedSink & to;
+    TunnelSource(Source & from, BufferedSink & to) : from(from), to(to) { }
+    size_t readUnbuffered(unsigned char * data, size_t len) override
+    {
+        to << STDERR_READ << len;
+        to.flush();
+        size_t n = readString(data, len, from);
+        if (n == 0) throw EndOfFile("unexpected end-of-file");
+        return n;
+    }
+};
+
+/* If the NAR archive contains a single file at top-level, then save
+   the contents of the file to `s'.  Otherwise barf. */
+struct RetrieveRegularNARSink : ParseSink
+{
+    bool regular;
+    string s;
+
+    RetrieveRegularNARSink() : regular(true) { }
+
+    void createDirectory(const Path & path)
+    {
+        regular = false;
+    }
+
+    void receiveContents(unsigned char * data, unsigned int len)
+    {
+        s.append((const char *) data, len);
+    }
+
+    void createSymlink(const Path & path, const string & target)
+    {
+        regular = false;
+    }
+};
+
+static void performOp(TunnelLogger * logger, ref<Store> store,
+    bool trusted, unsigned int clientVersion,
+    Source & from, BufferedSink & to, unsigned int op)
+{
+    switch (op) {
+
+    case wopIsValidPath: {
+        /* 'readStorePath' could raise an error leading to the connection
+           being closed.  To be able to recover from an invalid path error,
+           call 'startWork' early, and do 'assertStorePath' afterwards so
+           that the 'Error' exception handler doesn't close the
+           connection.  */
+        Path path = readString(from);
+        logger->startWork();
+        store->assertStorePath(path);
+        bool result = store->isValidPath(path);
+        logger->stopWork();
+        to << result;
+        break;
+    }
+
+    case wopQueryValidPaths: {
+        PathSet paths = readStorePaths<PathSet>(*store, from);
+        logger->startWork();
+        PathSet res = store->queryValidPaths(paths);
+        logger->stopWork();
+        to << res;
+        break;
+    }
+
+    case wopHasSubstitutes: {
+        Path path = readStorePath(*store, from);
+        logger->startWork();
+        PathSet res = store->querySubstitutablePaths({path});
+        logger->stopWork();
+        to << (res.find(path) != res.end());
+        break;
+    }
+
+    case wopQuerySubstitutablePaths: {
+        PathSet paths = readStorePaths<PathSet>(*store, from);
+        logger->startWork();
+        PathSet res = store->querySubstitutablePaths(paths);
+        logger->stopWork();
+        to << res;
+        break;
+    }
+
+    case wopQueryPathHash: {
+        Path path = readStorePath(*store, from);
+        logger->startWork();
+        auto hash = store->queryPathInfo(path)->narHash;
+        logger->stopWork();
+        to << hash.to_string(Base16, false);
+        break;
+    }
+
+    case wopQueryReferences:
+    case wopQueryReferrers:
+    case wopQueryValidDerivers:
+    case wopQueryDerivationOutputs: {
+        Path path = readStorePath(*store, from);
+        logger->startWork();
+        PathSet paths;
+        if (op == wopQueryReferences)
+            paths = store->queryPathInfo(path)->references;
+        else if (op == wopQueryReferrers)
+            store->queryReferrers(path, paths);
+        else if (op == wopQueryValidDerivers)
+            paths = store->queryValidDerivers(path);
+        else paths = store->queryDerivationOutputs(path);
+        logger->stopWork();
+        to << paths;
+        break;
+    }
+
+    case wopQueryDerivationOutputNames: {
+        Path path = readStorePath(*store, from);
+        logger->startWork();
+        StringSet names;
+        names = store->queryDerivationOutputNames(path);
+        logger->stopWork();
+        to << names;
+        break;
+    }
+
+    case wopQueryDeriver: {
+        Path path = readStorePath(*store, from);
+        logger->startWork();
+        auto deriver = store->queryPathInfo(path)->deriver;
+        logger->stopWork();
+        to << deriver;
+        break;
+    }
+
+    case wopQueryPathFromHashPart: {
+        string hashPart = readString(from);
+        logger->startWork();
+        Path path = store->queryPathFromHashPart(hashPart);
+        logger->stopWork();
+        to << path;
+        break;
+    }
+
+    case wopAddToStore: {
+        bool fixed, recursive;
+        std::string s, baseName;
+        from >> baseName >> fixed /* obsolete */ >> recursive >> s;
+        /* Compatibility hack. */
+        if (!fixed) {
+            s = "sha256";
+            recursive = true;
+        }
+        HashType hashAlgo = parseHashType(s);
+
+        TeeSource savedNAR(from);
+        RetrieveRegularNARSink savedRegular;
+
+        if (recursive) {
+            /* Get the entire NAR dump from the client and save it to
+               a string so that we can pass it to
+               addToStoreFromDump(). */
+            ParseSink sink; /* null sink; just parse the NAR */
+            parseDump(sink, savedNAR);
+        } else
+            parseDump(savedRegular, from);
+
+        logger->startWork();
+        if (!savedRegular.regular) throw Error("regular file expected");
+
+        Path path = store->addToStoreFromDump(recursive ? *savedNAR.data : savedRegular.s, baseName, recursive, hashAlgo);
+        logger->stopWork();
+
+        to << path;
+        break;
+    }
+
+    case wopAddTextToStore: {
+        string suffix = readString(from);
+        string s = readString(from);
+        PathSet refs = readStorePaths<PathSet>(*store, from);
+        logger->startWork();
+        Path path = store->addTextToStore(suffix, s, refs, NoRepair);
+        logger->stopWork();
+        to << path;
+        break;
+    }
+
+    case wopExportPath: {
+        Path path = readStorePath(*store, from);
+        readInt(from); // obsolete
+        logger->startWork();
+        TunnelSink sink(to);
+        store->exportPath(path, sink);
+        logger->stopWork();
+        to << 1;
+        break;
+    }
+
+    case wopImportPaths: {
+        logger->startWork();
+        TunnelSource source(from, to);
+        Paths paths = store->importPaths(source, nullptr,
+            trusted ? NoCheckSigs : CheckSigs);
+        logger->stopWork();
+        to << paths;
+        break;
+    }
+
+    case wopBuildPaths: {
+        PathSet drvs = readStorePaths<PathSet>(*store, from);
+        BuildMode mode = bmNormal;
+        if (GET_PROTOCOL_MINOR(clientVersion) >= 15) {
+            mode = (BuildMode) readInt(from);
+
+            /* Repairing is not atomic, so disallowed for "untrusted"
+               clients.  */
+            if (mode == bmRepair && !trusted)
+                throw Error("repairing is not allowed because you are not in 'trusted-users'");
+        }
+        logger->startWork();
+        store->buildPaths(drvs, mode);
+        logger->stopWork();
+        to << 1;
+        break;
+    }
+
+    case wopBuildDerivation: {
+        Path drvPath = readStorePath(*store, from);
+        BasicDerivation drv;
+        readDerivation(from, *store, drv);
+        BuildMode buildMode = (BuildMode) readInt(from);
+        logger->startWork();
+        if (!trusted)
+            throw Error("you are not privileged to build derivations");
+        auto res = store->buildDerivation(drvPath, drv, buildMode);
+        logger->stopWork();
+        to << res.status << res.errorMsg;
+        break;
+    }
+
+    case wopEnsurePath: {
+        Path path = readStorePath(*store, from);
+        logger->startWork();
+        store->ensurePath(path);
+        logger->stopWork();
+        to << 1;
+        break;
+    }
+
+    case wopAddTempRoot: {
+        Path path = readStorePath(*store, from);
+        logger->startWork();
+        store->addTempRoot(path);
+        logger->stopWork();
+        to << 1;
+        break;
+    }
+
+    case wopAddIndirectRoot: {
+        Path path = absPath(readString(from));
+        logger->startWork();
+        store->addIndirectRoot(path);
+        logger->stopWork();
+        to << 1;
+        break;
+    }
+
+    case wopSyncWithGC: {
+        logger->startWork();
+        store->syncWithGC();
+        logger->stopWork();
+        to << 1;
+        break;
+    }
+
+    case wopFindRoots: {
+        logger->startWork();
+        Roots roots = store->findRoots(!trusted);
+        logger->stopWork();
+
+        size_t size = 0;
+        for (auto & i : roots)
+            size += i.second.size();
+
+        to << size;
+
+        for (auto & [target, links] : roots)
+            for (auto & link : links)
+                to << link << target;
+
+        break;
+    }
+
+    case wopCollectGarbage: {
+        GCOptions options;
+        options.action = (GCOptions::GCAction) readInt(from);
+        options.pathsToDelete = readStorePaths<PathSet>(*store, from);
+        from >> options.ignoreLiveness >> options.maxFreed;
+        // obsolete fields
+        readInt(from);
+        readInt(from);
+        readInt(from);
+
+        GCResults results;
+
+        logger->startWork();
+        if (options.ignoreLiveness)
+            throw Error("you are not allowed to ignore liveness");
+        store->collectGarbage(options, results);
+        logger->stopWork();
+
+        to << results.paths << results.bytesFreed << 0 /* obsolete */;
+
+        break;
+    }
+
+    case wopSetOptions: {
+        settings.keepFailed = readInt(from);
+        settings.keepGoing = readInt(from);
+        settings.tryFallback = readInt(from);
+        verbosity = (Verbosity) readInt(from);
+        settings.maxBuildJobs.assign(readInt(from));
+        settings.maxSilentTime = readInt(from);
+        readInt(from); // obsolete useBuildHook
+        settings.verboseBuild = lvlError == (Verbosity) readInt(from);
+        readInt(from); // obsolete logType
+        readInt(from); // obsolete printBuildTrace
+        settings.buildCores = readInt(from);
+        settings.useSubstitutes  = readInt(from);
+
+        StringMap overrides;
+        if (GET_PROTOCOL_MINOR(clientVersion) >= 12) {
+            unsigned int n = readInt(from);
+            for (unsigned int i = 0; i < n; i++) {
+                string name = readString(from);
+                string value = readString(from);
+                overrides.emplace(name, value);
+            }
+        }
+
+        logger->startWork();
+
+        for (auto & i : overrides) {
+            auto & name(i.first);
+            auto & value(i.second);
+
+            auto setSubstituters = [&](Setting<Strings> & res) {
+                if (name != res.name && res.aliases.count(name) == 0)
+                    return false;
+                StringSet trusted = settings.trustedSubstituters;
+                for (auto & s : settings.substituters.get())
+                    trusted.insert(s);
+                Strings subs;
+                auto ss = tokenizeString<Strings>(value);
+                for (auto & s : ss)
+                    if (trusted.count(s))
+                        subs.push_back(s);
+                    else
+                        warn("ignoring untrusted substituter '%s'", s);
+                res = subs;
+                return true;
+            };
+
+            try {
+                if (name == "ssh-auth-sock") // obsolete
+                    ;
+                else if (trusted
+                    || name == settings.buildTimeout.name
+                    || name == "connect-timeout"
+                    || (name == "builders" && value == ""))
+                    settings.set(name, value);
+                else if (setSubstituters(settings.substituters))
+                    ;
+                else if (setSubstituters(settings.extraSubstituters))
+                    ;
+                else
+                    warn("ignoring the user-specified setting '%s', because it is a restricted setting and you are not a trusted user", name);
+            } catch (UsageError & e) {
+                warn(e.what());
+            }
+        }
+
+        logger->stopWork();
+        break;
+    }
+
+    case wopQuerySubstitutablePathInfo: {
+        Path path = absPath(readString(from));
+        logger->startWork();
+        SubstitutablePathInfos infos;
+        store->querySubstitutablePathInfos({path}, infos);
+        logger->stopWork();
+        SubstitutablePathInfos::iterator i = infos.find(path);
+        if (i == infos.end())
+            to << 0;
+        else {
+            to << 1 << i->second.deriver << i->second.references << i->second.downloadSize << i->second.narSize;
+        }
+        break;
+    }
+
+    case wopQuerySubstitutablePathInfos: {
+        PathSet paths = readStorePaths<PathSet>(*store, from);
+        logger->startWork();
+        SubstitutablePathInfos infos;
+        store->querySubstitutablePathInfos(paths, infos);
+        logger->stopWork();
+        to << infos.size();
+        for (auto & i : infos) {
+            to << i.first << i.second.deriver << i.second.references
+               << i.second.downloadSize << i.second.narSize;
+        }
+        break;
+    }
+
+    case wopQueryAllValidPaths: {
+        logger->startWork();
+        PathSet paths = store->queryAllValidPaths();
+        logger->stopWork();
+        to << paths;
+        break;
+    }
+
+    case wopQueryPathInfo: {
+        Path path = readStorePath(*store, from);
+        std::shared_ptr<const ValidPathInfo> info;
+        logger->startWork();
+        try {
+            info = store->queryPathInfo(path);
+        } catch (InvalidPath &) {
+            if (GET_PROTOCOL_MINOR(clientVersion) < 17) throw;
+        }
+        logger->stopWork();
+        if (info) {
+            if (GET_PROTOCOL_MINOR(clientVersion) >= 17)
+                to << 1;
+            to << info->deriver << info->narHash.to_string(Base16, false) << info->references
+               << info->registrationTime << info->narSize;
+            if (GET_PROTOCOL_MINOR(clientVersion) >= 16) {
+                to << info->ultimate
+                   << info->sigs
+                   << info->ca;
+            }
+        } else {
+            assert(GET_PROTOCOL_MINOR(clientVersion) >= 17);
+            to << 0;
+        }
+        break;
+    }
+
+    case wopOptimiseStore:
+        logger->startWork();
+        store->optimiseStore();
+        logger->stopWork();
+        to << 1;
+        break;
+
+    case wopVerifyStore: {
+        bool checkContents, repair;
+        from >> checkContents >> repair;
+        logger->startWork();
+        if (repair && !trusted)
+            throw Error("you are not privileged to repair paths");
+        bool errors = store->verifyStore(checkContents, (RepairFlag) repair);
+        logger->stopWork();
+        to << errors;
+        break;
+    }
+
+    case wopAddSignatures: {
+        Path path = readStorePath(*store, from);
+        StringSet sigs = readStrings<StringSet>(from);
+        logger->startWork();
+        if (!trusted)
+            throw Error("you are not privileged to add signatures");
+        store->addSignatures(path, sigs);
+        logger->stopWork();
+        to << 1;
+        break;
+    }
+
+    case wopNarFromPath: {
+        auto path = readStorePath(*store, from);
+        logger->startWork();
+        logger->stopWork();
+        dumpPath(path, to);
+        break;
+    }
+
+    case wopAddToStoreNar: {
+        bool repair, dontCheckSigs;
+        ValidPathInfo info;
+        info.path = readStorePath(*store, from);
+        from >> info.deriver;
+        if (!info.deriver.empty())
+            store->assertStorePath(info.deriver);
+        info.narHash = Hash(readString(from), htSHA256);
+        info.references = readStorePaths<PathSet>(*store, from);
+        from >> info.registrationTime >> info.narSize >> info.ultimate;
+        info.sigs = readStrings<StringSet>(from);
+        from >> info.ca >> repair >> dontCheckSigs;
+        if (!trusted && dontCheckSigs)
+            dontCheckSigs = false;
+        if (!trusted)
+            info.ultimate = false;
+
+        std::string saved;
+        std::unique_ptr<Source> source;
+        if (GET_PROTOCOL_MINOR(clientVersion) >= 21)
+            source = std::make_unique<TunnelSource>(from, to);
+        else {
+            TeeSink tee(from);
+            parseDump(tee, tee.source);
+            saved = std::move(*tee.source.data);
+            source = std::make_unique<StringSource>(saved);
+        }
+
+        logger->startWork();
+
+        // FIXME: race if addToStore doesn't read source?
+        store->addToStore(info, *source, (RepairFlag) repair,
+            dontCheckSigs ? NoCheckSigs : CheckSigs, nullptr);
+
+        logger->stopWork();
+        break;
+    }
+
+    case wopQueryMissing: {
+        PathSet targets = readStorePaths<PathSet>(*store, from);
+        logger->startWork();
+        PathSet willBuild, willSubstitute, unknown;
+        unsigned long long downloadSize, narSize;
+        store->queryMissing(targets, willBuild, willSubstitute, unknown, downloadSize, narSize);
+        logger->stopWork();
+        to << willBuild << willSubstitute << unknown << downloadSize << narSize;
+        break;
+    }
+
+    default:
+        throw Error(format("invalid operation %1%") % op);
+    }
+}
+
+void processConnection(
+    ref<Store> store,
+    FdSource & from,
+    FdSink & to,
+    bool trusted,
+    const std::string & userName,
+    uid_t userId)
+{
+    MonitorFdHup monitor(from.fd);
+
+    /* Exchange the greeting. */
+    unsigned int magic = readInt(from);
+    if (magic != WORKER_MAGIC_1) throw Error("protocol mismatch");
+    to << WORKER_MAGIC_2 << PROTOCOL_VERSION;
+    to.flush();
+    unsigned int clientVersion = readInt(from);
+
+    if (clientVersion < 0x10a)
+        throw Error("the Nix client version is too old");
+
+    auto tunnelLogger = new TunnelLogger(to, clientVersion);
+    auto prevLogger = nix::logger;
+    logger = tunnelLogger;
+
+    unsigned int opCount = 0;
+
+    Finally finally([&]() {
+        _isInterrupted = false;
+        prevLogger->log(lvlDebug, fmt("%d operations", opCount));
+    });
+
+    if (GET_PROTOCOL_MINOR(clientVersion) >= 14 && readInt(from))
+        setAffinityTo(readInt(from));
+
+    readInt(from); // obsolete reserveSpace
+
+    /* Send startup error messages to the client. */
+    tunnelLogger->startWork();
+
+    try {
+
+        /* If we can't accept clientVersion, then throw an error
+           *here* (not above). */
+
+#if 0
+        /* Prevent users from doing something very dangerous. */
+        if (geteuid() == 0 &&
+            querySetting("build-users-group", "") == "")
+            throw Error("if you run 'nix-daemon' as root, then you MUST set 'build-users-group'!");
+#endif
+
+        store->createUser(userName, userId);
+
+        tunnelLogger->stopWork();
+        to.flush();
+
+        /* Process client requests. */
+        while (true) {
+            WorkerOp op;
+            try {
+                op = (WorkerOp) readInt(from);
+            } catch (Interrupted & e) {
+                break;
+            } catch (EndOfFile & e) {
+                break;
+            }
+
+            opCount++;
+
+            try {
+                performOp(tunnelLogger, store, trusted, clientVersion, from, to, op);
+            } catch (Error & e) {
+                /* If we're not in a state where we can send replies, then
+                   something went wrong processing the input of the
+                   client.  This can happen especially if I/O errors occur
+                   during addTextToStore() / importPath().  If that
+                   happens, just send the error message and exit. */
+                bool errorAllowed = tunnelLogger->state_.lock()->canSendStderr;
+                tunnelLogger->stopWork(false, e.msg(), e.status);
+                if (!errorAllowed) throw;
+            } catch (std::bad_alloc & e) {
+                tunnelLogger->stopWork(false, "Nix daemon out of memory", 1);
+                throw;
+            }
+
+            to.flush();
+
+            assert(!tunnelLogger->state_.lock()->canSendStderr);
+        };
+
+    } catch (std::exception & e) {
+        tunnelLogger->stopWork(false, e.what(), 1);
+        to.flush();
+        return;
+    }
+}
+
+}
diff --git a/src/libstore/daemon.hh b/src/libstore/daemon.hh
new file mode 100644
index 000000000..fa26ba9c2
--- /dev/null
+++ b/src/libstore/daemon.hh
@@ -0,0 +1,14 @@
+#include "serialise.hh"
+#include "store-api.hh"
+
+namespace nix::daemon {
+
+void processConnection(
+    ref<Store> store,
+    FdSource & from,
+    FdSink & to,
+    bool trusted,
+    const std::string & userName,
+    uid_t userId);
+
+}
diff --git a/src/libstore/legacy-ssh-store.cc b/src/libstore/legacy-ssh-store.cc
index d5fbdd25a..1b8b5908c 100644
--- a/src/libstore/legacy-ssh-store.cc
+++ b/src/libstore/legacy-ssh-store.cc
@@ -88,7 +88,7 @@ struct LegacySSHStore : public Store
     }
 
     void queryPathInfoUncached(const Path & path,
-        Callback<std::shared_ptr<ValidPathInfo>> callback) noexcept override
+        Callback<std::shared_ptr<const ValidPathInfo>> callback) noexcept override
     {
         try {
             auto conn(connections->get());
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 4807f5800..46e8138be 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -625,7 +625,7 @@ uint64_t LocalStore::addValidPath(State & state,
 
 
 void LocalStore::queryPathInfoUncached(const Path & path,
-    Callback<std::shared_ptr<ValidPathInfo>> callback) noexcept
+    Callback<std::shared_ptr<const ValidPathInfo>> callback) noexcept
 {
     try {
         auto info = std::make_shared<ValidPathInfo>();
@@ -930,8 +930,7 @@ void LocalStore::registerValidPaths(const ValidPathInfos & infos)
            not be valid yet. */
         for (auto & i : infos)
             if (isDerivation(i.path)) {
-                // FIXME: inefficient; we already loaded the
-                // derivation in addValidPath().
+                // FIXME: inefficient; we already loaded the derivation in addValidPath().
                 Derivation drv = readDerivation(realStoreDir + "/" + baseNameOf(i.path));
                 checkDerivationOutputs(i.path, drv);
             }
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index 379a06af8..5aa6b0519 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -127,7 +127,7 @@ public:
     PathSet queryAllValidPaths() override;
 
     void queryPathInfoUncached(const Path & path,
-        Callback<std::shared_ptr<ValidPathInfo>> callback) noexcept override;
+        Callback<std::shared_ptr<const ValidPathInfo>> callback) noexcept override;
 
     void queryReferrers(const Path & path, PathSet & referrers) override;
 
@@ -157,7 +157,7 @@ public:
        true) or simply the contents of a regular file (if recursive ==
        false). */
     Path addToStoreFromDump(const string & dump, const string & name,
-        bool recursive = true, HashType hashAlgo = htSHA256, RepairFlag repair = NoRepair);
+        bool recursive = true, HashType hashAlgo = htSHA256, RepairFlag repair = NoRepair) override;
 
     Path addTextToStore(const string & name, const string & s,
         const PathSet & references, RepairFlag repair) override;
diff --git a/src/libstore/misc.cc b/src/libstore/misc.cc
index 05b93d4c9..2fceb9b9a 100644
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -33,7 +33,7 @@ void Store::computeFSClosure(const PathSet & startPaths,
             state->pending++;
         }
 
-        queryPathInfo(path, {[&, path](std::future<ref<ValidPathInfo>> fut) {
+        queryPathInfo(path, {[&, path](std::future<ref<const ValidPathInfo>> fut) {
             // FIXME: calls to isValidPath() should be async
 
             try {
diff --git a/src/libstore/nar-info-disk-cache.cc b/src/libstore/nar-info-disk-cache.cc
index 3f6dbbcf5..37c4c72e0 100644
--- a/src/libstore/nar-info-disk-cache.cc
+++ b/src/libstore/nar-info-disk-cache.cc
@@ -214,7 +214,7 @@ public:
 
     void upsertNarInfo(
         const std::string & uri, const std::string & hashPart,
-        std::shared_ptr<ValidPathInfo> info) override
+        std::shared_ptr<const ValidPathInfo> info) override
     {
         retrySQLite<void>([&]() {
             auto state(_state.lock());
@@ -223,7 +223,7 @@ public:
 
             if (info) {
 
-                auto narInfo = std::dynamic_pointer_cast<NarInfo>(info);
+                auto narInfo = std::dynamic_pointer_cast<const NarInfo>(info);
 
                 assert(hashPart == storePathToHash(info->path));
 
diff --git a/src/libstore/nar-info-disk-cache.hh b/src/libstore/nar-info-disk-cache.hh
index 0646d5a94..fb34f8c93 100644
--- a/src/libstore/nar-info-disk-cache.hh
+++ b/src/libstore/nar-info-disk-cache.hh
@@ -23,7 +23,7 @@ public:
 
     virtual void upsertNarInfo(
         const std::string & uri, const std::string & hashPart,
-        std::shared_ptr<ValidPathInfo> info) = 0;
+        std::shared_ptr<const ValidPathInfo> info) = 0;
 };
 
 /* Return a singleton cache object that can be used concurrently by
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index f34369d8f..2a89b7c98 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -350,7 +350,7 @@ void RemoteStore::querySubstitutablePathInfos(const PathSet & paths,
 
 
 void RemoteStore::queryPathInfoUncached(const Path & path,
-    Callback<std::shared_ptr<ValidPathInfo>> callback) noexcept
+    Callback<std::shared_ptr<const ValidPathInfo>> callback) noexcept
 {
     try {
         std::shared_ptr<ValidPathInfo> info;
diff --git a/src/libstore/remote-store.hh b/src/libstore/remote-store.hh
index 1f375dd71..84de4c460 100644
--- a/src/libstore/remote-store.hh
+++ b/src/libstore/remote-store.hh
@@ -43,7 +43,7 @@ public:
     PathSet queryAllValidPaths() override;
 
     void queryPathInfoUncached(const Path & path,
-        Callback<std::shared_ptr<ValidPathInfo>> callback) noexcept override;
+        Callback<std::shared_ptr<const ValidPathInfo>> callback) noexcept override;
 
     void queryReferrers(const Path & path, PathSet & referrers) override;
 
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index ef8b9575f..ea91bf20e 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -320,10 +320,10 @@ bool Store::isValidPathUncached(const Path & path)
 
 ref<const ValidPathInfo> Store::queryPathInfo(const Path & storePath)
 {
-    std::promise<ref<ValidPathInfo>> promise;
+    std::promise<ref<const ValidPathInfo>> promise;
 
     queryPathInfo(storePath,
-        {[&](std::future<ref<ValidPathInfo>> result) {
+        {[&](std::future<ref<const ValidPathInfo>> result) {
             try {
                 promise.set_value(result.get());
             } catch (...) {
@@ -336,7 +336,7 @@ ref<const ValidPathInfo> Store::queryPathInfo(const Path & storePath)
 
 
 void Store::queryPathInfo(const Path & storePath,
-    Callback<ref<ValidPathInfo>> callback) noexcept
+    Callback<ref<const ValidPathInfo>> callback) noexcept
 {
     std::string hashPart;
 
@@ -351,7 +351,7 @@ void Store::queryPathInfo(const Path & storePath,
                 stats.narInfoReadAverted++;
                 if (!*res)
                     throw InvalidPath(format("path '%s' is not valid") % storePath);
-                return callback(ref<ValidPathInfo>(*res));
+                return callback(ref<const ValidPathInfo>(*res));
             }
         }
 
@@ -367,7 +367,7 @@ void Store::queryPathInfo(const Path & storePath,
                         (res.second->path != storePath && storePathToName(storePath) != ""))
                         throw InvalidPath(format("path '%s' is not valid") % storePath);
                 }
-                return callback(ref<ValidPathInfo>(res.second));
+                return callback(ref<const ValidPathInfo>(res.second));
             }
         }
 
@@ -376,7 +376,7 @@ void Store::queryPathInfo(const Path & storePath,
     auto callbackPtr = std::make_shared<decltype(callback)>(std::move(callback));
 
     queryPathInfoUncached(storePath,
-        {[this, storePath, hashPart, callbackPtr](std::future<std::shared_ptr<ValidPathInfo>> fut) {
+        {[this, storePath, hashPart, callbackPtr](std::future<std::shared_ptr<const ValidPathInfo>> fut) {
 
             try {
                 auto info = fut.get();
@@ -396,7 +396,7 @@ void Store::queryPathInfo(const Path & storePath,
                     throw InvalidPath("path '%s' is not valid", storePath);
                 }
 
-                (*callbackPtr)(ref<ValidPathInfo>(info));
+                (*callbackPtr)(ref<const ValidPathInfo>(info));
             } catch (...) { callbackPtr->rethrow(); }
         }});
 }
@@ -418,7 +418,7 @@ PathSet Store::queryValidPaths(const PathSet & paths, SubstituteFlag maybeSubsti
 
     auto doQuery = [&](const Path & path ) {
         checkInterrupt();
-        queryPathInfo(path, {[path, &state_, &wakeup](std::future<ref<ValidPathInfo>> fut) {
+        queryPathInfo(path, {[path, &state_, &wakeup](std::future<ref<const ValidPathInfo>> fut) {
             auto state(state_.lock());
             try {
                 auto info = fut.get();
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 0a0bb9a83..814ec8d29 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -259,7 +259,7 @@ protected:
 
     struct State
     {
-        LRUCache<std::string, std::shared_ptr<ValidPathInfo>> pathInfoCache;
+        LRUCache<std::string, std::shared_ptr<const ValidPathInfo>> pathInfoCache;
     };
 
     Sync<State> state;
@@ -362,12 +362,12 @@ public:
 
     /* Asynchronous version of queryPathInfo(). */
     void queryPathInfo(const Path & path,
-        Callback<ref<ValidPathInfo>> callback) noexcept;
+        Callback<ref<const ValidPathInfo>> callback) noexcept;
 
 protected:
 
     virtual void queryPathInfoUncached(const Path & path,
-        Callback<std::shared_ptr<ValidPathInfo>> callback) noexcept = 0;
+        Callback<std::shared_ptr<const ValidPathInfo>> callback) noexcept = 0;
 
 public:
 
@@ -423,6 +423,13 @@ public:
         bool recursive = true, HashType hashAlgo = htSHA256,
         PathFilter & filter = defaultPathFilter, RepairFlag repair = NoRepair) = 0;
 
+    // FIXME: remove?
+    virtual Path addToStoreFromDump(const string & dump, const string & name,
+        bool recursive = true, HashType hashAlgo = htSHA256, RepairFlag repair = NoRepair)
+    {
+        throw Error("addToStoreFromDump() is not supported by this store");
+    }
+
     /* Like addToStore, but the contents written to the output path is
        a regular file containing the given string. */
     virtual Path addTextToStore(const string & name, const string & s,
diff --git a/src/libstore/worker-protocol.hh b/src/libstore/worker-protocol.hh
index 5ebdfaf13..6762b609d 100644
--- a/src/libstore/worker-protocol.hh
+++ b/src/libstore/worker-protocol.hh
@@ -62,6 +62,9 @@ typedef enum {
 #define STDERR_RESULT         0x52534c54
 
 
+class Store;
+struct Source;
+
 Path readStorePath(Store & store, Source & from);
 template<class T> T readStorePaths(Store & store, Source & from);
 
diff --git a/src/libutil/archive.cc b/src/libutil/archive.cc
index 3aa120270..db544a212 100644
--- a/src/libutil/archive.cc
+++ b/src/libutil/archive.cc
@@ -375,4 +375,13 @@ void copyNAR(Source & source, Sink & sink)
 }
 
 
+void copyPath(const Path & from, const Path & to)
+{
+    auto source = sinkToSource([&](Sink & sink) {
+        dumpPath(from, sink);
+    });
+    restorePath(to, *source);
+}
+
+
 }
diff --git a/src/libutil/archive.hh b/src/libutil/archive.hh
index 25be426c1..768fe2536 100644
--- a/src/libutil/archive.hh
+++ b/src/libutil/archive.hh
@@ -77,6 +77,8 @@ void restorePath(const Path & path, Source & source);
 /* Read a NAR from 'source' and write it to 'sink'. */
 void copyNAR(Source & source, Sink & sink);
 
+void copyPath(const Path & from, const Path & to);
+
 
 extern const std::string narVersionMagic1;
 
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 7c06cf166..747b31cff 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -21,8 +21,10 @@
 #include <pwd.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
+#include <sys/socket.h>
 #include <sys/wait.h>
 #include <sys/time.h>
+#include <sys/un.h>
 #include <unistd.h>
 
 #ifdef __APPLE__
@@ -1470,7 +1472,7 @@ static Sync<std::pair<unsigned short, unsigned short>> windowSize{{0, 0}};
 static void updateWindowSize()
 {
     struct winsize ws;
-    if (ioctl(1, TIOCGWINSZ, &ws) == 0) {
+    if (ioctl(2, TIOCGWINSZ, &ws) == 0) {
         auto windowSize_(windowSize.lock());
         windowSize_->first = ws.ws_row;
         windowSize_->second = ws.ws_col;
@@ -1567,4 +1569,33 @@ std::unique_ptr<InterruptCallback> createInterruptCallback(std::function<void()>
     return std::unique_ptr<InterruptCallback>(res.release());
 }
 
+
+AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode)
+{
+    AutoCloseFD fdSocket = socket(PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+    if (!fdSocket)
+        throw SysError("cannot create Unix domain socket");
+
+    closeOnExec(fdSocket.get());
+
+    struct sockaddr_un addr;
+    addr.sun_family = AF_UNIX;
+    if (path.size() >= sizeof(addr.sun_path))
+        throw Error("socket path '%1%' is too long", path);
+    strcpy(addr.sun_path, path.c_str());
+
+    unlink(path.c_str());
+
+    if (bind(fdSocket.get(), (struct sockaddr *) &addr, sizeof(addr)) == -1)
+        throw SysError("cannot bind to socket '%1%'", path);
+
+    if (chmod(path.c_str(), mode) == -1)
+        throw SysError("changing permissions on '%1%'", path);
+
+    if (listen(fdSocket.get(), 5) == -1)
+        throw SysError("cannot listen on socket '%1%'", path);
+
+    return fdSocket;
+}
+
 }
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 30654e315..2e5f4ca4e 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -577,4 +577,8 @@ typedef std::function<bool(const Path & path)> PathFilter;
 extern PathFilter defaultPathFilter;
 
 
+/* Create a Unix domain socket in listen mode. */
+AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode);
+
+
 }
diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index 50909608a..45db2f699 100755
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -245,7 +245,17 @@ static void _main(int argc, char * * argv)
     auto state = std::make_unique<EvalState>(myArgs.searchPath, store);
     state->repair = repair;
 
-    Bindings & autoArgs = *myArgs.getAutoArgs(*state);
+    auto autoArgs = myArgs.getAutoArgs(*state);
+
+    if (runEnv) {
+        auto newArgs = state->allocBindings(autoArgs->size() + 1);
+        auto tru = state->allocValue();
+        mkBool(*tru, true);
+        newArgs->push_back(Attr(state->symbols.create("inNixShell"), tru));
+        for (auto & i : *autoArgs) newArgs->push_back(i);
+        newArgs->sort();
+        autoArgs = newArgs;
+    }
 
     if (packages) {
         std::ostringstream joined;
@@ -299,9 +309,9 @@ static void _main(int argc, char * * argv)
         state->eval(e, vRoot);
 
         for (auto & i : attrPaths) {
-            Value & v(*findAlongAttrPath(*state, i, autoArgs, vRoot));
+            Value & v(*findAlongAttrPath(*state, i, *autoArgs, vRoot));
             state->forceValue(v);
-            getDerivations(*state, v, "", autoArgs, drvs, false);
+            getDerivations(*state, v, "", *autoArgs, drvs, false);
         }
     }
 
diff --git a/src/nix-daemon/nix-daemon.cc b/src/nix-daemon/nix-daemon.cc
index cd18489b0..da17ddcba 100644
--- a/src/nix-daemon/nix-daemon.cc
+++ b/src/nix-daemon/nix-daemon.cc
@@ -2,14 +2,12 @@
 #include "local-store.hh"
 #include "util.hh"
 #include "serialise.hh"
-#include "worker-protocol.hh"
 #include "archive.hh"
-#include "affinity.hh"
 #include "globals.hh"
-#include "monitor-fd.hh"
 #include "derivations.hh"
 #include "finally.hh"
 #include "legacy.hh"
+#include "daemon.hh"
 
 #include <algorithm>
 
@@ -32,6 +30,7 @@
 #endif
 
 using namespace nix;
+using namespace nix::daemon;
 
 #ifndef __linux__
 #define SPLICE_F_MOVE 0
@@ -53,793 +52,6 @@ static ssize_t splice(int fd_in, void *off_in, int fd_out, void *off_out, size_t
 }
 #endif
 
-static FdSource from(STDIN_FILENO);
-static FdSink to(STDOUT_FILENO);
-
-
-Sink & operator << (Sink & sink, const Logger::Fields & fields)
-{
-    sink << fields.size();
-    for (auto & f : fields) {
-        sink << f.type;
-        if (f.type == Logger::Field::tInt)
-            sink << f.i;
-        else if (f.type == Logger::Field::tString)
-            sink << f.s;
-        else abort();
-    }
-    return sink;
-}
-
-
-/* Logger that forwards log messages to the client, *if* we're in a
-   state where the protocol allows it (i.e., when canSendStderr is
-   true). */
-struct TunnelLogger : public Logger
-{
-    struct State
-    {
-        bool canSendStderr = false;
-        std::vector<std::string> pendingMsgs;
-    };
-
-    Sync<State> state_;
-
-    unsigned int clientVersion;
-
-    TunnelLogger(unsigned int clientVersion) : clientVersion(clientVersion) { }
-
-    void enqueueMsg(const std::string & s)
-    {
-        auto state(state_.lock());
-
-        if (state->canSendStderr) {
-            assert(state->pendingMsgs.empty());
-            try {
-                to(s);
-                to.flush();
-            } catch (...) {
-                /* Write failed; that means that the other side is
-                   gone. */
-                state->canSendStderr = false;
-                throw;
-            }
-        } else
-            state->pendingMsgs.push_back(s);
-    }
-
-    void log(Verbosity lvl, const FormatOrString & fs) override
-    {
-        if (lvl > verbosity) return;
-
-        StringSink buf;
-        buf << STDERR_NEXT << (fs.s + "\n");
-        enqueueMsg(*buf.s);
-    }
-
-    /* startWork() means that we're starting an operation for which we
-      want to send out stderr to the client. */
-    void startWork()
-    {
-        auto state(state_.lock());
-        state->canSendStderr = true;
-
-        for (auto & msg : state->pendingMsgs)
-            to(msg);
-
-        state->pendingMsgs.clear();
-
-        to.flush();
-    }
-
-    /* stopWork() means that we're done; stop sending stderr to the
-       client. */
-    void stopWork(bool success = true, const string & msg = "", unsigned int status = 0)
-    {
-        auto state(state_.lock());
-
-        state->canSendStderr = false;
-
-        if (success)
-            to << STDERR_LAST;
-        else {
-            to << STDERR_ERROR << msg;
-            if (status != 0) to << status;
-        }
-    }
-
-    void startActivity(ActivityId act, Verbosity lvl, ActivityType type,
-        const std::string & s, const Fields & fields, ActivityId parent) override
-    {
-        if (GET_PROTOCOL_MINOR(clientVersion) < 20) {
-            if (!s.empty())
-                log(lvl, s + "...");
-            return;
-        }
-
-        StringSink buf;
-        buf << STDERR_START_ACTIVITY << act << lvl << type << s << fields << parent;
-        enqueueMsg(*buf.s);
-    }
-
-    void stopActivity(ActivityId act) override
-    {
-        if (GET_PROTOCOL_MINOR(clientVersion) < 20) return;
-        StringSink buf;
-        buf << STDERR_STOP_ACTIVITY << act;
-        enqueueMsg(*buf.s);
-    }
-
-    void result(ActivityId act, ResultType type, const Fields & fields) override
-    {
-        if (GET_PROTOCOL_MINOR(clientVersion) < 20) return;
-        StringSink buf;
-        buf << STDERR_RESULT << act << type << fields;
-        enqueueMsg(*buf.s);
-    }
-};
-
-
-struct TunnelSink : Sink
-{
-    Sink & to;
-    TunnelSink(Sink & to) : to(to) { }
-    virtual void operator () (const unsigned char * data, size_t len)
-    {
-        to << STDERR_WRITE;
-        writeString(data, len, to);
-    }
-};
-
-
-struct TunnelSource : BufferedSource
-{
-    Source & from;
-    TunnelSource(Source & from) : from(from) { }
-protected:
-    size_t readUnbuffered(unsigned char * data, size_t len) override
-    {
-        to << STDERR_READ << len;
-        to.flush();
-        size_t n = readString(data, len, from);
-        if (n == 0) throw EndOfFile("unexpected end-of-file");
-        return n;
-    }
-};
-
-
-/* If the NAR archive contains a single file at top-level, then save
-   the contents of the file to `s'.  Otherwise barf. */
-struct RetrieveRegularNARSink : ParseSink
-{
-    bool regular;
-    string s;
-
-    RetrieveRegularNARSink() : regular(true) { }
-
-    void createDirectory(const Path & path)
-    {
-        regular = false;
-    }
-
-    void receiveContents(unsigned char * data, unsigned int len)
-    {
-        s.append((const char *) data, len);
-    }
-
-    void createSymlink(const Path & path, const string & target)
-    {
-        regular = false;
-    }
-};
-
-
-static void performOp(TunnelLogger * logger, ref<Store> store,
-    bool trusted, unsigned int clientVersion,
-    Source & from, Sink & to, unsigned int op)
-{
-    switch (op) {
-
-    case wopIsValidPath: {
-        /* 'readStorePath' could raise an error leading to the connection
-           being closed.  To be able to recover from an invalid path error,
-           call 'startWork' early, and do 'assertStorePath' afterwards so
-           that the 'Error' exception handler doesn't close the
-           connection.  */
-        Path path = readString(from);
-        logger->startWork();
-        store->assertStorePath(path);
-        bool result = store->isValidPath(path);
-        logger->stopWork();
-        to << result;
-        break;
-    }
-
-    case wopQueryValidPaths: {
-        PathSet paths = readStorePaths<PathSet>(*store, from);
-        logger->startWork();
-        PathSet res = store->queryValidPaths(paths);
-        logger->stopWork();
-        to << res;
-        break;
-    }
-
-    case wopHasSubstitutes: {
-        Path path = readStorePath(*store, from);
-        logger->startWork();
-        PathSet res = store->querySubstitutablePaths({path});
-        logger->stopWork();
-        to << (res.find(path) != res.end());
-        break;
-    }
-
-    case wopQuerySubstitutablePaths: {
-        PathSet paths = readStorePaths<PathSet>(*store, from);
-        logger->startWork();
-        PathSet res = store->querySubstitutablePaths(paths);
-        logger->stopWork();
-        to << res;
-        break;
-    }
-
-    case wopQueryPathHash: {
-        Path path = readStorePath(*store, from);
-        logger->startWork();
-        auto hash = store->queryPathInfo(path)->narHash;
-        logger->stopWork();
-        to << hash.to_string(Base16, false);
-        break;
-    }
-
-    case wopQueryReferences:
-    case wopQueryReferrers:
-    case wopQueryValidDerivers:
-    case wopQueryDerivationOutputs: {
-        Path path = readStorePath(*store, from);
-        logger->startWork();
-        PathSet paths;
-        if (op == wopQueryReferences)
-            paths = store->queryPathInfo(path)->references;
-        else if (op == wopQueryReferrers)
-            store->queryReferrers(path, paths);
-        else if (op == wopQueryValidDerivers)
-            paths = store->queryValidDerivers(path);
-        else paths = store->queryDerivationOutputs(path);
-        logger->stopWork();
-        to << paths;
-        break;
-    }
-
-    case wopQueryDerivationOutputNames: {
-        Path path = readStorePath(*store, from);
-        logger->startWork();
-        StringSet names;
-        names = store->queryDerivationOutputNames(path);
-        logger->stopWork();
-        to << names;
-        break;
-    }
-
-    case wopQueryDeriver: {
-        Path path = readStorePath(*store, from);
-        logger->startWork();
-        auto deriver = store->queryPathInfo(path)->deriver;
-        logger->stopWork();
-        to << deriver;
-        break;
-    }
-
-    case wopQueryPathFromHashPart: {
-        string hashPart = readString(from);
-        logger->startWork();
-        Path path = store->queryPathFromHashPart(hashPart);
-        logger->stopWork();
-        to << path;
-        break;
-    }
-
-    case wopAddToStore: {
-        bool fixed, recursive;
-        std::string s, baseName;
-        from >> baseName >> fixed /* obsolete */ >> recursive >> s;
-        /* Compatibility hack. */
-        if (!fixed) {
-            s = "sha256";
-            recursive = true;
-        }
-        HashType hashAlgo = parseHashType(s);
-
-        TeeSource savedNAR(from);
-        RetrieveRegularNARSink savedRegular;
-
-        if (recursive) {
-            /* Get the entire NAR dump from the client and save it to
-               a string so that we can pass it to
-               addToStoreFromDump(). */
-            ParseSink sink; /* null sink; just parse the NAR */
-            parseDump(sink, savedNAR);
-        } else
-            parseDump(savedRegular, from);
-
-        logger->startWork();
-        if (!savedRegular.regular) throw Error("regular file expected");
-
-        auto store2 = store.dynamic_pointer_cast<LocalStore>();
-        if (!store2) throw Error("operation is only supported by LocalStore");
-
-        Path path = store2->addToStoreFromDump(recursive ? *savedNAR.data : savedRegular.s, baseName, recursive, hashAlgo);
-        logger->stopWork();
-
-        to << path;
-        break;
-    }
-
-    case wopAddTextToStore: {
-        string suffix = readString(from);
-        string s = readString(from);
-        PathSet refs = readStorePaths<PathSet>(*store, from);
-        logger->startWork();
-        Path path = store->addTextToStore(suffix, s, refs, NoRepair);
-        logger->stopWork();
-        to << path;
-        break;
-    }
-
-    case wopExportPath: {
-        Path path = readStorePath(*store, from);
-        readInt(from); // obsolete
-        logger->startWork();
-        TunnelSink sink(to);
-        store->exportPath(path, sink);
-        logger->stopWork();
-        to << 1;
-        break;
-    }
-
-    case wopImportPaths: {
-        logger->startWork();
-        TunnelSource source(from);
-        Paths paths = store->importPaths(source, nullptr,
-            trusted ? NoCheckSigs : CheckSigs);
-        logger->stopWork();
-        to << paths;
-        break;
-    }
-
-    case wopBuildPaths: {
-        PathSet drvs = readStorePaths<PathSet>(*store, from);
-        BuildMode mode = bmNormal;
-        if (GET_PROTOCOL_MINOR(clientVersion) >= 15) {
-            mode = (BuildMode) readInt(from);
-
-            /* Repairing is not atomic, so disallowed for "untrusted"
-               clients.  */
-            if (mode == bmRepair && !trusted)
-                throw Error("repairing is not allowed because you are not in 'trusted-users'");
-        }
-        logger->startWork();
-        store->buildPaths(drvs, mode);
-        logger->stopWork();
-        to << 1;
-        break;
-    }
-
-    case wopBuildDerivation: {
-        Path drvPath = readStorePath(*store, from);
-        BasicDerivation drv;
-        readDerivation(from, *store, drv);
-        BuildMode buildMode = (BuildMode) readInt(from);
-        logger->startWork();
-        if (!trusted)
-            throw Error("you are not privileged to build derivations");
-        auto res = store->buildDerivation(drvPath, drv, buildMode);
-        logger->stopWork();
-        to << res.status << res.errorMsg;
-        break;
-    }
-
-    case wopEnsurePath: {
-        Path path = readStorePath(*store, from);
-        logger->startWork();
-        store->ensurePath(path);
-        logger->stopWork();
-        to << 1;
-        break;
-    }
-
-    case wopAddTempRoot: {
-        Path path = readStorePath(*store, from);
-        logger->startWork();
-        store->addTempRoot(path);
-        logger->stopWork();
-        to << 1;
-        break;
-    }
-
-    case wopAddIndirectRoot: {
-        Path path = absPath(readString(from));
-        logger->startWork();
-        store->addIndirectRoot(path);
-        logger->stopWork();
-        to << 1;
-        break;
-    }
-
-    case wopSyncWithGC: {
-        logger->startWork();
-        store->syncWithGC();
-        logger->stopWork();
-        to << 1;
-        break;
-    }
-
-    case wopFindRoots: {
-        logger->startWork();
-        Roots roots = store->findRoots(!trusted);
-        logger->stopWork();
-
-        size_t size = 0;
-        for (auto & i : roots)
-            size += i.second.size();
-
-        to << size;
-
-        for (auto & [target, links] : roots)
-            for (auto & link : links)
-                to << link << target;
-
-        break;
-    }
-
-    case wopCollectGarbage: {
-        GCOptions options;
-        options.action = (GCOptions::GCAction) readInt(from);
-        options.pathsToDelete = readStorePaths<PathSet>(*store, from);
-        from >> options.ignoreLiveness >> options.maxFreed;
-        // obsolete fields
-        readInt(from);
-        readInt(from);
-        readInt(from);
-
-        GCResults results;
-
-        logger->startWork();
-        if (options.ignoreLiveness)
-            throw Error("you are not allowed to ignore liveness");
-        store->collectGarbage(options, results);
-        logger->stopWork();
-
-        to << results.paths << results.bytesFreed << 0 /* obsolete */;
-
-        break;
-    }
-
-    case wopSetOptions: {
-        settings.keepFailed = readInt(from);
-        settings.keepGoing = readInt(from);
-        settings.tryFallback = readInt(from);
-        verbosity = (Verbosity) readInt(from);
-        settings.maxBuildJobs.assign(readInt(from));
-        settings.maxSilentTime = readInt(from);
-        readInt(from); // obsolete useBuildHook
-        settings.verboseBuild = lvlError == (Verbosity) readInt(from);
-        readInt(from); // obsolete logType
-        readInt(from); // obsolete printBuildTrace
-        settings.buildCores = readInt(from);
-        settings.useSubstitutes  = readInt(from);
-
-        StringMap overrides;
-        if (GET_PROTOCOL_MINOR(clientVersion) >= 12) {
-            unsigned int n = readInt(from);
-            for (unsigned int i = 0; i < n; i++) {
-                string name = readString(from);
-                string value = readString(from);
-                overrides.emplace(name, value);
-            }
-        }
-
-        logger->startWork();
-
-        for (auto & i : overrides) {
-            auto & name(i.first);
-            auto & value(i.second);
-
-            auto setSubstituters = [&](Setting<Strings> & res) {
-                if (name != res.name && res.aliases.count(name) == 0)
-                    return false;
-                StringSet trusted = settings.trustedSubstituters;
-                for (auto & s : settings.substituters.get())
-                    trusted.insert(s);
-                Strings subs;
-                auto ss = tokenizeString<Strings>(value);
-                for (auto & s : ss)
-                    if (trusted.count(s))
-                        subs.push_back(s);
-                    else
-                        warn("ignoring untrusted substituter '%s'", s);
-                res = subs;
-                return true;
-            };
-
-            try {
-                if (name == "ssh-auth-sock") // obsolete
-                    ;
-                else if (trusted
-                    || name == settings.buildTimeout.name
-                    || name == "connect-timeout"
-                    || (name == "builders" && value == ""))
-                    settings.set(name, value);
-                else if (setSubstituters(settings.substituters))
-                    ;
-                else if (setSubstituters(settings.extraSubstituters))
-                    ;
-                else
-                    warn("ignoring the user-specified setting '%s', because it is a restricted setting and you are not a trusted user", name);
-            } catch (UsageError & e) {
-                warn(e.what());
-            }
-        }
-
-        logger->stopWork();
-        break;
-    }
-
-    case wopQuerySubstitutablePathInfo: {
-        Path path = absPath(readString(from));
-        logger->startWork();
-        SubstitutablePathInfos infos;
-        store->querySubstitutablePathInfos({path}, infos);
-        logger->stopWork();
-        SubstitutablePathInfos::iterator i = infos.find(path);
-        if (i == infos.end())
-            to << 0;
-        else {
-            to << 1 << i->second.deriver << i->second.references << i->second.downloadSize << i->second.narSize;
-        }
-        break;
-    }
-
-    case wopQuerySubstitutablePathInfos: {
-        PathSet paths = readStorePaths<PathSet>(*store, from);
-        logger->startWork();
-        SubstitutablePathInfos infos;
-        store->querySubstitutablePathInfos(paths, infos);
-        logger->stopWork();
-        to << infos.size();
-        for (auto & i : infos) {
-            to << i.first << i.second.deriver << i.second.references
-               << i.second.downloadSize << i.second.narSize;
-        }
-        break;
-    }
-
-    case wopQueryAllValidPaths: {
-        logger->startWork();
-        PathSet paths = store->queryAllValidPaths();
-        logger->stopWork();
-        to << paths;
-        break;
-    }
-
-    case wopQueryPathInfo: {
-        Path path = readStorePath(*store, from);
-        std::shared_ptr<const ValidPathInfo> info;
-        logger->startWork();
-        try {
-            info = store->queryPathInfo(path);
-        } catch (InvalidPath &) {
-            if (GET_PROTOCOL_MINOR(clientVersion) < 17) throw;
-        }
-        logger->stopWork();
-        if (info) {
-            if (GET_PROTOCOL_MINOR(clientVersion) >= 17)
-                to << 1;
-            to << info->deriver << info->narHash.to_string(Base16, false) << info->references
-               << info->registrationTime << info->narSize;
-            if (GET_PROTOCOL_MINOR(clientVersion) >= 16) {
-                to << info->ultimate
-                   << info->sigs
-                   << info->ca;
-            }
-        } else {
-            assert(GET_PROTOCOL_MINOR(clientVersion) >= 17);
-            to << 0;
-        }
-        break;
-    }
-
-    case wopOptimiseStore:
-        logger->startWork();
-        store->optimiseStore();
-        logger->stopWork();
-        to << 1;
-        break;
-
-    case wopVerifyStore: {
-        bool checkContents, repair;
-        from >> checkContents >> repair;
-        logger->startWork();
-        if (repair && !trusted)
-            throw Error("you are not privileged to repair paths");
-        bool errors = store->verifyStore(checkContents, (RepairFlag) repair);
-        logger->stopWork();
-        to << errors;
-        break;
-    }
-
-    case wopAddSignatures: {
-        Path path = readStorePath(*store, from);
-        StringSet sigs = readStrings<StringSet>(from);
-        logger->startWork();
-        if (!trusted)
-            throw Error("you are not privileged to add signatures");
-        store->addSignatures(path, sigs);
-        logger->stopWork();
-        to << 1;
-        break;
-    }
-
-    case wopNarFromPath: {
-        auto path = readStorePath(*store, from);
-        logger->startWork();
-        logger->stopWork();
-        dumpPath(path, to);
-        break;
-    }
-
-    case wopAddToStoreNar: {
-        bool repair, dontCheckSigs;
-        ValidPathInfo info;
-        info.path = readStorePath(*store, from);
-        from >> info.deriver;
-        if (!info.deriver.empty())
-            store->assertStorePath(info.deriver);
-        info.narHash = Hash(readString(from), htSHA256);
-        info.references = readStorePaths<PathSet>(*store, from);
-        from >> info.registrationTime >> info.narSize >> info.ultimate;
-        info.sigs = readStrings<StringSet>(from);
-        from >> info.ca >> repair >> dontCheckSigs;
-        if (!trusted && dontCheckSigs)
-            dontCheckSigs = false;
-        if (!trusted)
-            info.ultimate = false;
-
-        std::string saved;
-        std::unique_ptr<Source> source;
-        if (GET_PROTOCOL_MINOR(clientVersion) >= 21)
-            source = std::make_unique<TunnelSource>(from);
-        else {
-            TeeSink tee(from);
-            parseDump(tee, tee.source);
-            saved = std::move(*tee.source.data);
-            source = std::make_unique<StringSource>(saved);
-        }
-
-        logger->startWork();
-
-        // FIXME: race if addToStore doesn't read source?
-        store->addToStore(info, *source, (RepairFlag) repair,
-            dontCheckSigs ? NoCheckSigs : CheckSigs, nullptr);
-
-        logger->stopWork();
-        break;
-    }
-
-    case wopQueryMissing: {
-        PathSet targets = readStorePaths<PathSet>(*store, from);
-        logger->startWork();
-        PathSet willBuild, willSubstitute, unknown;
-        unsigned long long downloadSize, narSize;
-        store->queryMissing(targets, willBuild, willSubstitute, unknown, downloadSize, narSize);
-        logger->stopWork();
-        to << willBuild << willSubstitute << unknown << downloadSize << narSize;
-        break;
-    }
-
-    default:
-        throw Error(format("invalid operation %1%") % op);
-    }
-}
-
-
-static void processConnection(bool trusted,
-    const std::string & userName, uid_t userId)
-{
-    MonitorFdHup monitor(from.fd);
-
-    /* Exchange the greeting. */
-    unsigned int magic = readInt(from);
-    if (magic != WORKER_MAGIC_1) throw Error("protocol mismatch");
-    to << WORKER_MAGIC_2 << PROTOCOL_VERSION;
-    to.flush();
-    unsigned int clientVersion = readInt(from);
-
-    if (clientVersion < 0x10a)
-        throw Error("the Nix client version is too old");
-
-    auto tunnelLogger = new TunnelLogger(clientVersion);
-    auto prevLogger = nix::logger;
-    logger = tunnelLogger;
-
-    unsigned int opCount = 0;
-
-    Finally finally([&]() {
-        _isInterrupted = false;
-        prevLogger->log(lvlDebug, fmt("%d operations", opCount));
-    });
-
-    if (GET_PROTOCOL_MINOR(clientVersion) >= 14 && readInt(from))
-        setAffinityTo(readInt(from));
-
-    readInt(from); // obsolete reserveSpace
-
-    /* Send startup error messages to the client. */
-    tunnelLogger->startWork();
-
-    try {
-
-        /* If we can't accept clientVersion, then throw an error
-           *here* (not above). */
-
-#if 0
-        /* Prevent users from doing something very dangerous. */
-        if (geteuid() == 0 &&
-            querySetting("build-users-group", "") == "")
-            throw Error("if you run 'nix-daemon' as root, then you MUST set 'build-users-group'!");
-#endif
-
-        /* Open the store. */
-        Store::Params params; // FIXME: get params from somewhere
-        // Disable caching since the client already does that.
-        params["path-info-cache-size"] = "0";
-        auto store = openStore(settings.storeUri, params);
-
-        store->createUser(userName, userId);
-
-        tunnelLogger->stopWork();
-        to.flush();
-
-        /* Process client requests. */
-        while (true) {
-            WorkerOp op;
-            try {
-                op = (WorkerOp) readInt(from);
-            } catch (Interrupted & e) {
-                break;
-            } catch (EndOfFile & e) {
-                break;
-            }
-
-            opCount++;
-
-            try {
-                performOp(tunnelLogger, store, trusted, clientVersion, from, to, op);
-            } catch (Error & e) {
-                /* If we're not in a state where we can send replies, then
-                   something went wrong processing the input of the
-                   client.  This can happen especially if I/O errors occur
-                   during addTextToStore() / importPath().  If that
-                   happens, just send the error message and exit. */
-                bool errorAllowed = tunnelLogger->state_.lock()->canSendStderr;
-                tunnelLogger->stopWork(false, e.msg(), e.status);
-                if (!errorAllowed) throw;
-            } catch (std::bad_alloc & e) {
-                tunnelLogger->stopWork(false, "Nix daemon out of memory", 1);
-                throw;
-            }
-
-            to.flush();
-
-            assert(!tunnelLogger->state_.lock()->canSendStderr);
-        };
-
-    } catch (std::exception & e) {
-        tunnelLogger->stopWork(false, e.what(), 1);
-        to.flush();
-        return;
-    }
-}
-
 
 static void sigChldHandler(int sigNo)
 {
@@ -928,6 +140,15 @@ static PeerInfo getPeerInfo(int remote)
 #define SD_LISTEN_FDS_START 3
 
 
+static ref<Store> openUncachedStore()
+{
+    Store::Params params; // FIXME: get params from somewhere
+    // Disable caching since the client already does that.
+    params["path-info-cache-size"] = "0";
+    return openStore(settings.storeUri, params);
+}
+
+
 static void daemonLoop(char * * argv)
 {
     if (chdir("/") == -1)
@@ -944,53 +165,15 @@ static void daemonLoop(char * * argv)
         if (getEnv("LISTEN_PID") != std::to_string(getpid()) || getEnv("LISTEN_FDS") != "1")
             throw Error("unexpected systemd environment variables");
         fdSocket = SD_LISTEN_FDS_START;
+        closeOnExec(fdSocket.get());
     }
 
     /* Otherwise, create and bind to a Unix domain socket. */
     else {
-
-        /* Create and bind to a Unix domain socket. */
-        fdSocket = socket(PF_UNIX, SOCK_STREAM, 0);
-        if (!fdSocket)
-            throw SysError("cannot create Unix domain socket");
-
-        string socketPath = settings.nixDaemonSocketFile;
-
-        createDirs(dirOf(socketPath));
-
-        /* Urgh, sockaddr_un allows path names of only 108 characters.
-           So chdir to the socket directory so that we can pass a
-           relative path name. */
-        if (chdir(dirOf(socketPath).c_str()) == -1)
-            throw SysError("cannot change current directory");
-        Path socketPathRel = "./" + baseNameOf(socketPath);
-
-        struct sockaddr_un addr;
-        addr.sun_family = AF_UNIX;
-        if (socketPathRel.size() >= sizeof(addr.sun_path))
-            throw Error(format("socket path '%1%' is too long") % socketPathRel);
-        strcpy(addr.sun_path, socketPathRel.c_str());
-
-        unlink(socketPath.c_str());
-
-        /* Make sure that the socket is created with 0666 permission
-           (everybody can connect --- provided they have access to the
-           directory containing the socket). */
-        mode_t oldMode = umask(0111);
-        int res = bind(fdSocket.get(), (struct sockaddr *) &addr, sizeof(addr));
-        umask(oldMode);
-        if (res == -1)
-            throw SysError(format("cannot bind to socket '%1%'") % socketPath);
-
-        if (chdir("/") == -1) /* back to the root */
-            throw SysError("cannot change current directory");
-
-        if (listen(fdSocket.get(), 5) == -1)
-            throw SysError(format("cannot listen on socket '%1%'") % socketPath);
+        createDirs(dirOf(settings.nixDaemonSocketFile));
+        fdSocket = createUnixDomainSocket(settings.nixDaemonSocketFile, 0666);
     }
 
-    closeOnExec(fdSocket.get());
-
     /* Loop accepting connections. */
     while (1) {
 
@@ -1054,9 +237,9 @@ static void daemonLoop(char * * argv)
                 }
 
                 /* Handle the connection. */
-                from.fd = remote.get();
-                to.fd = remote.get();
-                processConnection(trusted, user, peer.uid);
+                FdSource from(remote.get());
+                FdSink to(remote.get());
+                processConnection(openUncachedStore(), from, to, trusted, user, peer.uid);
 
                 exit(0);
             }, options);
@@ -1136,7 +319,9 @@ static int _main(int argc, char * * argv)
                     }
                 }
             } else {
-                processConnection(true, "root", 0);
+                FdSource from(STDIN_FILENO);
+                FdSink to(STDOUT_FILENO);
+                processConnection(openUncachedStore(), from, to, true, "root", 0);
             }
         } else {
             daemonLoop(argv);
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 19384499d..dfa473db5 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -632,8 +632,7 @@ static void opDelete(Strings opFlags, Strings opArgs)
 }
 
 
-/* Dump a path as a Nix archive.  The archive is written to standard
-   output. */
+/* Dump a path as a Nix archive.  The archive is written to stdout */
 static void opDump(Strings opFlags, Strings opArgs)
 {
     if (!opFlags.empty()) throw UsageError("unknown flag");
@@ -646,8 +645,7 @@ static void opDump(Strings opFlags, Strings opArgs)
 }
 
 
-/* Restore a value from a Nix archive.  The archive is read from
-   standard input. */
+/* Restore a value from a Nix archive.  The archive is read from stdin. */
 static void opRestore(Strings opFlags, Strings opArgs)
 {
     if (!opFlags.empty()) throw UsageError("unknown flag");
diff --git a/src/nix/command.hh b/src/nix/command.hh
index ef29381cf..13f3a0dc9 100644
--- a/src/nix/command.hh
+++ b/src/nix/command.hh
@@ -17,7 +17,7 @@ namespace flake {
 enum HandleLockFile : unsigned int;
 }
 
-/* A command that require a Nix store. */
+/* A command that requires a Nix store. */
 struct StoreCommand : virtual Command
 {
     StoreCommand();
@@ -91,6 +91,7 @@ private:
     std::vector<std::string> _installables;
 };
 
+/* A command that operates on exactly one "installable" */
 struct InstallableCommand : virtual Args, SourceExprCommand
 {
     std::shared_ptr<Installable> installable;
diff --git a/src/nix/eval.cc b/src/nix/eval.cc
index 524bac304..276fdf003 100644
--- a/src/nix/eval.cc
+++ b/src/nix/eval.cc
@@ -36,7 +36,7 @@ struct CmdEval : MixJSON, InstallableCommand
             },
             Example{
                 "To get the current version of Nixpkgs:",
-                "nix eval --raw nixpkgs.lib.nixpkgsVersion"
+                "nix eval --raw nixpkgs.lib.version"
             },
             Example{
                 "To print the store path of the Hello package:",
diff --git a/src/nix/main.cc b/src/nix/main.cc
index 8cdeed8f5..5c0faf879 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -15,6 +15,7 @@
 #include <sys/socket.h>
 #include <ifaddrs.h>
 #include <netdb.h>
+#include <netinet/in.h>
 
 extern std::string chrootHelperName;
 
diff --git a/src/nix/progress-bar.cc b/src/nix/progress-bar.cc
index 5c05d6b22..661966733 100644
--- a/src/nix/progress-bar.cc
+++ b/src/nix/progress-bar.cc
@@ -341,7 +341,7 @@ public:
         }
 
         auto width = getWindowSize().second;
-        if (width <= 0) std::numeric_limits<decltype(width)>::max();
+        if (width <= 0) width = std::numeric_limits<decltype(width)>::max();
 
         writeToStderr("\r" + filterANSIEscapes(line, false, width) + "\e[K");
     }