Add download-via-ssh substituter

This substituter connects to a remote host, runs nix-store --serve
there, and then forwards substituter commands on to the remote host and
sends their results to the calling program. The ssh-substituter-hosts
option can be specified as a list of hosts to try.

This is an initial implementation and, while it works, it has some
limitations:

* Only the first host is used
* There is no caching of query results (all queries are sent to the
  remote machine)
* There is no informative output (such as progress bars)
* Some failure modes may cause unhelpful error messages
* There is no concept of trusted-ssh-substituter-hosts

Signed-off-by: Shea Levy <shea@shealevy.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index 68add1982..c1ffc26fa 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -79,6 +79,7 @@ void Settings::processEnvironment()
 #endif
         substituters.push_back(nixLibexecDir + "/nix/substituters/download-using-manifests.pl");
         substituters.push_back(nixLibexecDir + "/nix/substituters/download-from-binary-cache.pl");
+        substituters.push_back(nixLibexecDir + "/nix/substituters/download-via-ssh");
     } else
         substituters = tokenizeString<Strings>(subs, ":");
 }
@@ -151,6 +152,7 @@ void Settings::update()
     get(gcKeepDerivations, "gc-keep-derivations");
     get(autoOptimiseStore, "auto-optimise-store");
     get(envKeepDerivations, "env-keep-derivations");
+    get(sshSubstituterHosts, "ssh-substituter-hosts");
 }
 
 
@@ -182,6 +184,13 @@ void Settings::get(StringSet & res, const string & name)
     res.insert(ss.begin(), ss.end());
 }
 
+void Settings::get(Strings & res, const string & name)
+{
+    SettingsMap::iterator i = settings.find(name);
+    if (i == settings.end()) return;
+    res = tokenizeString<Strings>(i->second);
+}
+
 
 template<class N> void Settings::get(N & res, const string & name)
 {
@@ -206,6 +215,17 @@ string Settings::pack()
 }
 
 
+void Settings::unpack(string pack) {
+    Strings lines = tokenizeString<Strings>(pack, "\n");
+    foreach (Strings::iterator, i, lines) {
+        string::size_type eq = i->find('=');
+        if (eq == string::npos)
+            throw Error("illegal option name/value");
+        set(i->substr(0, eq), i->substr(eq + 1));
+    }
+}
+
+
 Settings::SettingsMap Settings::getOverrides()
 {
     return overrides;