If we are to add/delete/change a route but have not yet daemonised,

flag that we are to track the parent pid.
On successful route message, remember the sequence number.
Once daemonised, ignore messages from the parent pid until we find
the saved sequence number - at this point remove the flag to track parent pid.

This fixes an issue where we didn't correctly ignore messages we generated
before forking but catching them in the child process.

1 files changed, 15 insertions, 6 deletions

diff --git a/dhcpcd.c b/dhcpcd.c
index aee3219a..9ac56c6b 100644
--- a/dhcpcd.c
+++ b/dhcpcd.c
@@ -322,29 +322,38 @@ dhcpcd_daemonise(struct dhcpcd_ctx *ctx)
 	if (ctx->options & DHCPCD_DAEMONISED ||
 	    !(ctx->options & DHCPCD_DAEMONISE))
 		return 0;
+	logger(ctx, LOG_DEBUG, "forking to background");
+
 	/* Setup a signal pipe so parent knows when to exit. */
 	if (pipe(sidpipe) == -1) {
 		logger(ctx, LOG_ERR, "pipe: %m");
 		return 0;
 	}
-	logger(ctx, LOG_DEBUG, "forking to background");
+
+	/* Store the pid and routing message seq number so we can identify
+	 * the last message successfully sent to the kernel.
+	 * This allows us to ignore all messages we sent after forking
+	 * and detaching. */
+	ctx->ppid = getpid();
+	ctx->pseq = ctx->sseq;
+
 	switch (pid = fork()) {
 	case -1:
 		logger(ctx, LOG_ERR, "fork: %m");
 		return 0;
 	case 0:
 		setsid();
+		/* Notify parent it's safe to exit as we've detached. */
+		close(sidpipe[0]);
+		if (write(sidpipe[1], &buf, 1) == -1)
+			logger(ctx, LOG_ERR, "failed to notify parent: %m");
+		close(sidpipe[1]);
 		/* Some polling methods don't survive after forking,
 		 * so ensure we can requeue all our events. */
 		if (eloop_requeue(ctx->eloop) == -1) {
 			logger(ctx, LOG_ERR, "eloop_requeue: %m");
 			eloop_exit(ctx->eloop, EXIT_FAILURE);
 		}
-		/* Notify parent it's safe to exit as we've detached. */
-		close(sidpipe[0]);
-		if (write(sidpipe[1], &buf, 1) == -1)
-			logger(ctx, LOG_ERR, "failed to notify parent: %m");
-		close(sidpipe[1]);
 		if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
 			dup2(fd, STDIN_FILENO);
 			dup2(fd, STDOUT_FILENO);