[lxc-devel] [PATCH] RFC: commands: handle epipe

[Serge Hallyn]

If we start a lxc_wait on a container while it is exiting, it is
possible that we open the command socket, then the monitor closes
all its mainloop sockets and exit, then we send our credentials.
Then we get killed by SIGPIPE.

Handle that case, recognizing that if we get sigpipe then the
container is (now) stopped.

Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
---
 src/lxc/af_unix.c  |  4 ++--
 src/lxc/commands.c | 11 ++++++++++-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/lxc/af_unix.c b/src/lxc/af_unix.c
index a2de73e..46d8e50 100644
--- a/src/lxc/af_unix.c
+++ b/src/lxc/af_unix.c
@@ -158,7 +158,7 @@ int lxc_abstract_unix_send_fd(int fd, int sendfd, void *data, size_t size)
 	msg.msg_iov = &iov;
 	msg.msg_iovlen = 1;
 
-	return sendmsg(fd, &msg, 0);
+	return sendmsg(fd, &msg, MSG_NOSIGNAL);
 }
 
 int lxc_abstract_unix_recv_fd(int fd, int *recvfd, void *data, size_t size)
@@ -230,7 +230,7 @@ int lxc_abstract_unix_send_credential(int fd, void *data, size_t size)
 	msg.msg_iov = &iov;
 	msg.msg_iovlen = 1;
 
-	return sendmsg(fd, &msg, 0);
+	return sendmsg(fd, &msg, MSG_NOSIGNAL);
 }
 
 int lxc_abstract_unix_rcv_credential(int fd, void *data, size_t size)
diff --git a/src/lxc/commands.c b/src/lxc/commands.c
index 6b46c2c..b71274c 100644
--- a/src/lxc/commands.c
+++ b/src/lxc/commands.c
@@ -263,6 +263,8 @@ static int lxc_cmd(const char *name, struct lxc_cmd_rr *cmd, int *stopped,
 
 	ret = lxc_abstract_unix_send_credential(sock, &cmd->req, sizeof(cmd->req));
 	if (ret != sizeof(cmd->req)) {
+		if (errno == EPIPE)
+			goto epipe;
 		SYSERROR("command %s failed to send req to '@%s' %d",
 			 lxc_cmd_str(cmd->req.cmd), offset, ret);
 		if (ret >=0)
@@ -271,8 +273,10 @@ static int lxc_cmd(const char *name, struct lxc_cmd_rr *cmd, int *stopped,
 	}
 
 	if (cmd->req.datalen > 0) {
-		ret = send(sock, cmd->req.data, cmd->req.datalen, 0);
+		ret = send(sock, cmd->req.data, cmd->req.datalen, MSG_NOSIGNAL);
 		if (ret != cmd->req.datalen) {
+			if (errno == EPIPE)
+				goto epipe;
 			SYSERROR("command %s failed to send request data to '@%s' %d",
 				 lxc_cmd_str(cmd->req.cmd), offset, ret);
 			if (ret >=0)
@@ -289,6 +293,11 @@ out:
 		cmd->rsp.ret = sock;
 
 	return ret;
+
+epipe:
+	close(sock);
+	*stopped = 1;
+	return 0;
 }
 
 int lxc_try_cmd(const char *name, const char *lxcpath)
-- 
1.9.1