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authorLudovic Courtès <ludo@gnu.org>2020-09-11 12:34:25 +0200
committerLudovic Courtès <ludo@gnu.org>2020-09-14 15:42:55 +0200
commitee9dff34f9317509cb2b833d07a0d5e01a36a4ae (patch)
tree47027d9453eb3fe69f61bdc31d6d480a20e1217a /nix/libutil/util.cc
parent27cc51c269fbe9d2ca65711d281c63ae441a9b4a (diff)
daemon: Move 'Agent' to libutil.
* nix/libstore/build.cc (DerivationGoal::tryBuildHook): Add "offload" to 'args' and pass settings.guixProgram as the first argument to Agent::Agent. (pathNullDevice, commonChildInit, Agent, Agent::Agent) (Agent::~Agent): Move to... * nix/libutil/util.cc: ... here. * nix/libutil/util.hh (struct Agent, commonChildInit): New declarations.
Diffstat (limited to 'nix/libutil/util.cc')
-rw-r--r--nix/libutil/util.cc84
1 files changed, 84 insertions, 0 deletions
diff --git a/nix/libutil/util.cc b/nix/libutil/util.cc
index 17d145b4c6..59a2981359 100644
--- a/nix/libutil/util.cc
+++ b/nix/libutil/util.cc
@@ -1142,5 +1142,89 @@ void ignoreException()
}
}
+static const string pathNullDevice = "/dev/null";
+
+/* Common initialisation performed in child processes. */
+void commonChildInit(Pipe & logPipe)
+{
+ /* Put the child in a separate session (and thus a separate
+ process group) so that it has no controlling terminal (meaning
+ that e.g. ssh cannot open /dev/tty) and it doesn't receive
+ terminal signals. */
+ if (setsid() == -1)
+ throw SysError(format("creating a new session"));
+
+ /* Dup the write side of the logger pipe into stderr. */
+ if (dup2(logPipe.writeSide, STDERR_FILENO) == -1)
+ throw SysError("cannot pipe standard error into log file");
+
+ /* Dup stderr to stdout. */
+ if (dup2(STDERR_FILENO, STDOUT_FILENO) == -1)
+ throw SysError("cannot dup stderr into stdout");
+
+ /* Reroute stdin to /dev/null. */
+ int fdDevNull = open(pathNullDevice.c_str(), O_RDWR);
+ if (fdDevNull == -1)
+ throw SysError(format("cannot open `%1%'") % pathNullDevice);
+ if (dup2(fdDevNull, STDIN_FILENO) == -1)
+ throw SysError("cannot dup null device into stdin");
+ close(fdDevNull);
+}
+
+//////////////////////////////////////////////////////////////////////
+
+Agent::Agent(const string &command, const Strings &args)
+{
+ debug(format("starting agent '%1%'") % command);
+
+ /* Create a pipe to get the output of the child. */
+ fromAgent.create();
+
+ /* Create the communication pipes. */
+ toAgent.create();
+
+ /* Create a pipe to get the output of the builder. */
+ builderOut.create();
+
+ /* Fork the hook. */
+ pid = startProcess([&]() {
+
+ commonChildInit(fromAgent);
+
+ if (chdir("/") == -1) throw SysError("changing into `/");
+
+ /* Dup the communication pipes. */
+ if (dup2(toAgent.readSide, STDIN_FILENO) == -1)
+ throw SysError("dupping to-hook read side");
+
+ /* Use fd 4 for the builder's stdout/stderr. */
+ if (dup2(builderOut.writeSide, 4) == -1)
+ throw SysError("dupping builder's stdout/stderr");
+
+ Strings allArgs;
+ allArgs.push_back(command);
+ allArgs.insert(allArgs.end(), args.begin(), args.end()); // append
+
+ execv(command.c_str(), stringsToCharPtrs(allArgs).data());
+
+ throw SysError(format("executing `%1%'") % command);
+ });
+
+ pid.setSeparatePG(true);
+ fromAgent.writeSide.close();
+ toAgent.readSide.close();
+}
+
+
+Agent::~Agent()
+{
+ try {
+ toAgent.writeSide.close();
+ pid.kill(true);
+ } catch (...) {
+ ignoreException();
+ }
+}
+
}