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Drop support for daemon socket path >= 108 characters

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Doing a chdir() is a bad idea in multi-threaded programs, leading to
failures such as

  error: cannot connect to daemon at ‘/nix/var/nix/daemon-socket/socket’: No such file or directory

Since Linux doesn't have a connectat() syscall like FreeBSD, there is
no way we can support this in a race-free way.
This commit is contained in:
Eelco Dolstra 2016-03-23 17:16:16 +01:00
parent 056b3ecfa4
commit c7d44bad00
1 changed files with 3 additions and 15 deletions
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18
src/libstore/remote-store.cc
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@ -61,27 +61,15 @@ ref<RemoteStore::Connection> RemoteStore::openConnection()
string socketPath = settings.nixDaemonSocketFile; string socketPath = settings.nixDaemonSocketFile;
/* 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. !!! this is probably a bad idea in multi-threaded
applications... */
AutoCloseFD fdPrevDir = open(".", O_RDONLY);
if (fdPrevDir == -1) throw SysError("couldn't open current directory");
if (chdir(dirOf(socketPath).c_str()) == -1) throw SysError(format("couldn't change to directory of ‘%1%’") % socketPath);
Path socketPathRel = "./" + baseNameOf(socketPath);
struct sockaddr_un addr; struct sockaddr_un addr;
addr.sun_family = AF_UNIX; addr.sun_family = AF_UNIX;
if (socketPathRel.size() >= sizeof(addr.sun_path)) if (socketPath.size() + 1 >= sizeof(addr.sun_path))
throw Error(format("socket path ‘%1%’ is too long") % socketPathRel); throw Error(format("socket path ‘%1%’ is too long") % socketPath);
strcpy(addr.sun_path, socketPathRel.c_str()); strcpy(addr.sun_path, socketPath.c_str());
if (connect(conn->fd, (struct sockaddr *) &addr, sizeof(addr)) == -1) if (connect(conn->fd, (struct sockaddr *) &addr, sizeof(addr)) == -1)
throw SysError(format("cannot connect to daemon at ‘%1%’") % socketPath); throw SysError(format("cannot connect to daemon at ‘%1%’") % socketPath);
if (fchdir(fdPrevDir) == -1)
throw SysError("couldn't change back to previous directory");
conn->from.fd = conn->fd; conn->from.fd = conn->fd;
conn->to.fd = conn->fd; conn->to.fd = conn->fd;