From c32c88b642b8c65eb68b505e0783fd46b57fc6fa Mon Sep 17 00:00:00 2001
From: Roy Marples <roy@marples.name>
Date: Wed, 8 Nov 2023 11:09:52 +0000
Subject: [PATCH] dhcpcd: Close fork_fd on hangup

Closing it early results in zero length reads in some situations.
Logging that we forked via the launcher process also make more sense
and allows us to use log* functions.

While here, handle error condtions better by forcing a return
rather than handling an invalid state.

Fixes #260.
---
 src/dhcpcd.c | 81 ++++++++++++++++++++++++++++++----------------------
 1 file changed, 47 insertions(+), 34 deletions(-)

diff --git a/src/dhcpcd.c b/src/dhcpcd.c
index 71e7d807..46c64b42 100644
--- a/src/dhcpcd.c
+++ b/src/dhcpcd.c
@@ -365,7 +365,6 @@ dhcpcd_daemonise(struct dhcpcd_ctx *ctx)
 	return;
 #else
 	int i;
-	unsigned int logopts = loggetopts();
 
 	if (ctx->options & DHCPCD_DAEMONISE &&
 	    !(ctx->options & (DHCPCD_DAEMONISED | DHCPCD_NOWAITIP)))
@@ -385,11 +384,6 @@ dhcpcd_daemonise(struct dhcpcd_ctx *ctx)
 	    !(ctx->options & DHCPCD_DAEMONISE))
 		return;
 
-	/* Don't use loginfo because this makes no sense in a log. */
-	if (!(logopts & LOGERR_QUIET) && ctx->stderr_valid)
-		(void)fprintf(stderr,
-		    "forked to background, child pid %d\n", getpid());
-
 #ifdef PRIVSEP
 	ps_daemonised(ctx);
 #else
@@ -400,9 +394,8 @@ dhcpcd_daemonise(struct dhcpcd_ctx *ctx)
 	if (write(ctx->fork_fd, &i, sizeof(i)) == -1)
 		logerr("write");
 	ctx->options |= DHCPCD_DAEMONISED;
-	eloop_event_delete(ctx->eloop, ctx->fork_fd);
-	close(ctx->fork_fd);
-	ctx->fork_fd = -1;
+	// dhcpcd_fork_cb will close the socket
+	shutdown(ctx->fork_fd, SHUT_RDWR);
 #endif
 }
 
@@ -1822,31 +1815,6 @@ dhcpcd_readdump(struct dhcpcd_ctx *ctx)
 	    dhcpcd_readdump0, ctx);
 }
 
-static void
-dhcpcd_fork_cb(void *arg, unsigned short events)
-{
-	struct dhcpcd_ctx *ctx = arg;
-	int exit_code;
-	ssize_t len;
-
-	if (!(events & ELE_READ))
-		logerrx("%s: unexpected event 0x%04x", __func__, events);
-
-	len = read(ctx->fork_fd, &exit_code, sizeof(exit_code));
-	if (len == -1) {
-		logerr(__func__);
-		exit_code = EXIT_FAILURE;
-	} else if ((size_t)len < sizeof(exit_code)) {
-		logerrx("%s: truncated read %zd (expected %zu)",
-		    __func__, len, sizeof(exit_code));
-		exit_code = EXIT_FAILURE;
-	}
-	if (ctx->options & DHCPCD_FORKED)
-		eloop_exit(ctx->eloop, exit_code);
-	else
-		dhcpcd_signal_cb(exit_code, ctx);
-}
-
 static void
 dhcpcd_stderr_cb(void *arg, unsigned short events)
 {
@@ -1871,6 +1839,51 @@ dhcpcd_stderr_cb(void *arg, unsigned short events)
 	fprintf(stderr, "%s", log);
 }
 
+static void
+dhcpcd_fork_cb(void *arg, unsigned short events)
+{
+	struct dhcpcd_ctx *ctx = arg;
+	int exit_code;
+	ssize_t len;
+
+	if (!(events & ELE_READ))
+		logerrx("%s: unexpected event 0x%04x", __func__, events);
+
+	len = read(ctx->fork_fd, &exit_code, sizeof(exit_code));
+	if (len == -1) {
+		logerr(__func__);
+		eloop_exit(ctx->eloop, EXIT_FAILURE);
+		return;
+	}
+	if (len == 0) {
+		if (ctx->options & DHCPCD_FORKED) {
+			logerrx("%s: dhcpcd manager hungup", __func__);
+			eloop_exit(ctx->eloop, EXIT_FAILURE);
+		} else {
+			// Launcher exited
+			eloop_event_delete(ctx->eloop, ctx->fork_fd);
+			close(ctx->fork_fd);
+			ctx->fork_fd = -1;
+		}
+		return;
+	}
+	if ((size_t)len < sizeof(exit_code)) {
+		logerrx("%s: truncated read %zd (expected %zu)",
+		    __func__, len, sizeof(exit_code));
+		eloop_exit(ctx->eloop, EXIT_FAILURE);
+		return;
+	}
+
+	if (ctx->options & DHCPCD_FORKED) {
+		if (exit_code == EXIT_SUCCESS)
+			logdebugx("forked to background");
+		else
+			logerrx("exited with code %d", exit_code);
+		eloop_exit(ctx->eloop, exit_code);
+	} else
+		dhcpcd_signal_cb(exit_code, ctx);
+}
+
 static void
 dhcpcd_pidfile_timeout(void *arg)
 {
-- 
2.47.2