Merge pull request #5335 from edolstra/socket-paths

Support arbitrary-length socket paths

4 files changed, 73 insertions, 25 deletions

diff --git a/src/libstore/uds-remote-store.cc b/src/libstore/uds-remote-store.cc
index cfadccf68..02e81b022 100644
--- a/src/libstore/uds-remote-store.cc
+++ b/src/libstore/uds-remote-store.cc
@@ -65,16 +65,7 @@ ref<RemoteStore::Connection> UDSRemoteStore::openConnection()
         throw SysError("cannot create Unix domain socket");
     closeOnExec(conn->fd.get());
 
-    string socketPath = path ? *path : settings.nixDaemonSocketFile;
-
-    struct sockaddr_un addr;
-    addr.sun_family = AF_UNIX;
-    if (socketPath.size() + 1 >= sizeof(addr.sun_path))
-        throw Error("socket path '%1%' is too long", socketPath);
-    strcpy(addr.sun_path, socketPath.c_str());
-
-    if (::connect(conn->fd.get(), (struct sockaddr *) &addr, sizeof(addr)) == -1)
-        throw SysError("cannot connect to daemon at '%1%'", socketPath);
+    nix::connect(conn->fd.get(), path ? *path : settings.nixDaemonSocketFile);
 
     conn->from.fd = conn->fd.get();
     conn->to.fd = conn->fd.get();
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index bc841f425..0b261ca60 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -903,7 +903,7 @@ int Pid::wait()
             return status;
         }
         if (errno != EINTR)
-            throw SysError("cannot get child exit status");
+            throw SysError("cannot get exit status of PID %d", pid);
         checkInterrupt();
     }
 }
@@ -1686,16 +1686,7 @@ AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode)
 
     closeOnExec(fdSocket.get());
 
-    struct sockaddr_un addr;
-    addr.sun_family = AF_UNIX;
-    if (path.size() + 1 >= 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);
+    bind(fdSocket.get(), path);
 
     if (chmod(path.c_str(), mode) == -1)
         throw SysError("changing permissions on '%1%'", path);
@@ -1707,6 +1698,66 @@ AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode)
 }
 
 
+void bind(int fd, const std::string & path)
+{
+    unlink(path.c_str());
+
+    struct sockaddr_un addr;
+    addr.sun_family = AF_UNIX;
+
+    if (path.size() + 1 >= sizeof(addr.sun_path)) {
+        Pid pid = startProcess([&]() {
+            auto dir = dirOf(path);
+            if (chdir(dir.c_str()) == -1)
+                throw SysError("chdir to '%s' failed", dir);
+            std::string base(baseNameOf(path));
+            if (base.size() + 1 >= sizeof(addr.sun_path))
+                throw Error("socket path '%s' is too long", base);
+            strcpy(addr.sun_path, base.c_str());
+            if (bind(fd, (struct sockaddr *) &addr, sizeof(addr)) == -1)
+                throw SysError("cannot bind to socket '%s'", path);
+            _exit(0);
+        });
+        int status = pid.wait();
+        if (status != 0)
+            throw Error("cannot bind to socket '%s'", path);
+    } else {
+        strcpy(addr.sun_path, path.c_str());
+        if (bind(fd, (struct sockaddr *) &addr, sizeof(addr)) == -1)
+            throw SysError("cannot bind to socket '%s'", path);
+    }
+}
+
+
+void connect(int fd, const std::string & path)
+{
+    struct sockaddr_un addr;
+    addr.sun_family = AF_UNIX;
+
+    if (path.size() + 1 >= sizeof(addr.sun_path)) {
+        Pid pid = startProcess([&]() {
+            auto dir = dirOf(path);
+            if (chdir(dir.c_str()) == -1)
+                throw SysError("chdir to '%s' failed", dir);
+            std::string base(baseNameOf(path));
+            if (base.size() + 1 >= sizeof(addr.sun_path))
+                throw Error("socket path '%s' is too long", base);
+            strcpy(addr.sun_path, base.c_str());
+            if (connect(fd, (struct sockaddr *) &addr, sizeof(addr)) == -1)
+                throw SysError("cannot connect to socket at '%s'", path);
+            _exit(0);
+        });
+        int status = pid.wait();
+        if (status != 0)
+            throw Error("cannot connect to socket at '%s'", path);
+    } else {
+        strcpy(addr.sun_path, path.c_str());
+        if (connect(fd, (struct sockaddr *) &addr, sizeof(addr)) == -1)
+            throw SysError("cannot connect to socket at '%s'", path);
+    }
+}
+
+
 string showBytes(uint64_t bytes)
 {
     return fmt("%.2f MiB", bytes / (1024.0 * 1024.0));
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index bee77b53f..6d3e64949 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -259,7 +259,7 @@ void killUser(uid_t uid);
    pid to the caller. */
 struct ProcessOptions
 {
-    string errorPrefix = "error: ";
+    string errorPrefix = "";
     bool dieWithParent = true;
     bool runExitHandlers = false;
     bool allowVfork = true;
@@ -574,6 +574,12 @@ void commonChildInit(Pipe & logPipe);
 /* Create a Unix domain socket in listen mode. */
 AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode);
 
+/* Bind a Unix domain socket to a path. */
+void bind(int fd, const std::string & path);
+
+/* Connect to a Unix domain socket. */
+void connect(int fd, const std::string & path);
+
 
 // A Rust/Python-like enumerate() iterator adapter.
 // Borrowed from http://reedbeta.com/blog/python-like-enumerate-in-cpp17.
diff --git a/src/nix/daemon.cc b/src/nix/daemon.cc
index 2cf2a04c9..6a40a0bd3 100644
--- a/src/nix/daemon.cc
+++ b/src/nix/daemon.cc
@@ -156,9 +156,6 @@ static void daemonLoop()
     if (chdir("/") == -1)
         throw SysError("cannot change current directory");
 
-    //  Get rid of children automatically; don't let them become zombies.
-    setSigChldAction(true);
-
     AutoCloseFD fdSocket;
 
     //  Handle socket-based activation by systemd.
@@ -176,6 +173,9 @@ static void daemonLoop()
         fdSocket = createUnixDomainSocket(settings.nixDaemonSocketFile, 0666);
     }
 
+    //  Get rid of children automatically; don't let them become zombies.
+    setSigChldAction(true);
+
     //  Loop accepting connections.
     while (1) {