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Support socket-based, on-demand activation of the Nix daemon with systemd

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Systemd can start the Nix daemon on demand when the Nix daemon socket
is first accessed.  This is signalled through the LISTEN_FDS
environment variable, so all we need to do is check for that and then
use file descriptor 3 as the listen socket instead of creating one
ourselves.
This commit is contained in:
Eelco Dolstra 2012-06-18 23:01:46 -04:00
parent 02fb6323e0
commit 2f3f413e91
1 changed files with 53 additions and 37 deletions
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88
src/nix-worker/nix-worker.cc
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@ -695,51 +695,67 @@ static void setSigChldAction(bool autoReap)
}
#define SD_LISTEN_FDS_START 3
static void daemonLoop()
{
/* Get rid of children automatically; don't let them become
zombies. */
setSigChldAction(true);
/* Create and bind to a Unix domain socket. */
AutoCloseFD fdSocket = socket(PF_UNIX, SOCK_STREAM, 0);
if (fdSocket == -1)
throw SysError("cannot create Unix domain socket");
AutoCloseFD fdSocket;
/* Handle socket-based activation by systemd. */
if (getEnv("LISTEN_FDS") != "") {
if (getEnv("LISTEN_PID") != int2String(getpid()) || getEnv("LISTEN_FDS") != "1")
throw Error("unexpected systemd environment variables");
fdSocket = SD_LISTEN_FDS_START;
}
/* 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 == -1)
throw SysError("cannot create Unix domain socket");
string socketPath = nixStateDir + DEFAULT_SOCKET_PATH;
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. */
chdir(dirOf(socketPath).c_str());
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, (struct sockaddr *) &addr, sizeof(addr));
umask(oldMode);
if (res == -1)
throw SysError(format("cannot bind to socket `%1%'") % socketPath);
chdir("/"); /* back to the root */
if (listen(fdSocket, 5) == -1)
throw SysError(format("cannot listen on socket `%1%'") % socketPath);
}
closeOnExec(fdSocket);
string socketPath = nixStateDir + DEFAULT_SOCKET_PATH;
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. */
chdir(dirOf(socketPath).c_str());
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, (struct sockaddr *) &addr, sizeof(addr));
umask(oldMode);
if (res == -1)
throw SysError(format("cannot bind to socket `%1%'") % socketPath);
chdir("/"); /* back to the root */
if (listen(fdSocket, 5) == -1)
throw SysError(format("cannot listen on socket `%1%'") % socketPath);
/* Loop accepting connections. */
while (1) {