mctpd: use SO_RCVTIMEO socket timeout

Instead of spawning an sd_event loop to wait for socket timeout, use
SO_RCVTIMEO socket option to implement socket timeout.

For tests, instead of implementing the timeout in the test runner, I
think we could use SO_RCVTIMEO on the control socket itself :^)

Signed-off-by: Khang D Nguyen <[email protected]>

Author: khangng-ampere

src/mctpd.c

@@ -471,50 +471,6 @@ static void *dfree(void *ptr)
 	return ptr;
 }
 
-static int cb_exit_loop_io(sd_event_source *s, int fd, uint32_t revents,
-			   void *userdata)
-{
-	sd_event_exit(sd_event_source_get_event(s), 0);
-	return 0;
-}
-
-static int cb_exit_loop_timeout(sd_event_source *s, uint64_t usec,
-				void *userdata)
-{
-	sd_event_exit(sd_event_source_get_event(s), -ETIMEDOUT);
-	return 0;
-}
-
-/* Events are EPOLLIN, EPOLLOUT etc.
-   Returns 0 on ready, negative on error. -ETIMEDOUT on timeout */
-static int wait_fd_timeout(int fd, short events, uint64_t timeout_usec)
-{
-	int rc;
-	sd_event *ev = NULL;
-
-	// Create a new event loop just for the event+timeout
-	rc = sd_event_new(&ev);
-	if (rc < 0)
-		goto out;
-
-	rc = sd_event_add_time_relative(ev, NULL, CLOCK_MONOTONIC, timeout_usec,
-					0, cb_exit_loop_timeout, NULL);
-	if (rc < 0)
-		goto out;
-
-	rc = sd_event_add_io(ev, NULL, fd, events, cb_exit_loop_io, NULL);
-	if (rc < 0)
-		goto out;
-
-	// TODO: maybe need to break the loop on SIGINT event too?
-	rc = sd_event_loop(ev);
-
-out:
-	if (ev)
-		sd_event_unref(ev);
-	return rc;
-}
-
 static const char *path_from_peer(const struct peer *peer)
 {
 	if (!peer->published) {
@@ -1521,6 +1477,7 @@ static int endpoint_query_addr(struct ctx *ctx,
 			       uint8_t **resp, size_t *resp_len,
 			       struct sockaddr_mctp_ext *resp_addr)
 {
+	struct timeval timeout;
 	size_t req_addr_len;
 	int sd = -1, val;
 	ssize_t rc;
@@ -1538,6 +1495,18 @@ static int endpoint_query_addr(struct ctx *ctx,
 		goto out;
 	}
 
+	static const long usec_per_sec = 1000000;
+	rc = mctp_ops.mctp.setsockopt(
+		sd, SOL_SOCKET, SO_RCVTIMEO,
+		&(struct timeval){
+			.tv_sec = ctx->mctp_timeout / usec_per_sec,
+			.tv_usec = ctx->mctp_timeout % usec_per_sec,
+		},
+		sizeof(timeout));
+	if (rc < 0) {
+		warn("Kernel does not support socket receive timeout");
+	}
+
 	// We want extended addressing on all received messages
 	val = 1;
 	rc = mctp_ops.mctp.setsockopt(sd, SOL_MCTP, MCTP_OPT_ADDR_EXT, &val,
@@ -1575,7 +1544,7 @@ static int endpoint_query_addr(struct ctx *ctx,
 		goto out;
 	}
 
-	rc = wait_fd_timeout(sd, EPOLLIN, ctx->mctp_timeout);
+	rc = read_message(ctx, sd, &buf, &buf_size, resp_addr);
 	if (rc < 0) {
 		if (rc == -ETIMEDOUT && ctx->verbose) {
 			warnx("%s: receive timed out from %s", __func__,
@@ -1584,11 +1553,6 @@ static int endpoint_query_addr(struct ctx *ctx,
 		goto out;
 	}
 
-	rc = read_message(ctx, sd, &buf, &buf_size, resp_addr);
-	if (rc < 0) {
-		goto out;
-	}
-
 	if (resp_addr->smctp_base.smctp_type !=
 	    req_addr->smctp_base.smctp_type) {
 		warnx("Mismatching response type %d for request type %d. dest %s",

tests/mctp-ops-test.c

@@ -117,6 +117,12 @@ static int mctp_op_setsockopt(int sd, int level, int optname, void *optval,
 	struct iovec iov[2];
 	ssize_t rc;
 
+	// For both real and stub socket descriptor, socket timeout can be handled by the kernel
+	// because we are not really doing anything
+	if (level == SOL_SOCKET && optname == SO_RCVTIMEO) {
+		return setsockopt(sd, level, optname, optval, optlen);
+	}
+
 	sock_msg.type = SOCK_SETSOCKOPT;
 	sock_msg.setsockopt.level = level;
 	sock_msg.setsockopt.optname = optname;