From: Valentine Krasnobaeva <vkrasnobaeva@haproxy.com>
Date: Thu, 3 Oct 2024 09:32:16 +0000 (+0200)
Subject: MINOR: mworker/cli: create master CLI sockpair before fork
X-Git-Tag: v3.1-dev10~34
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=6ec38c9a744fdba27961ceef16029402fff03697;p=thirdparty%2Fhaproxy.git

MINOR: mworker/cli: create master CLI sockpair before fork

The main idea here is to create a master CLI inherited sockpair just before the
master-worker fork. And only then after the fork let each process to bind a
needed listener to the its end of this sockpair.

Like this master and worker processes can close unused "ends" of its sockpair
copy (ipc_fd[0] for worker and and ipc_fd[1] for master).

When this sockpair creation happens inside the
mworker_cli_global_proxy_new_listener() is not possible for the master to
close ipc_fd[1] bound to the GLOBAL proxy listener, as this triggers a
BUG_ON(fd->owner) in fd_insert() in master context, because master process
has alredy entered in its polling loop and poller in its turn tries to reused
closed fd.
---

diff --git a/src/cli.c b/src/cli.c
index e60113d927..bbd11c1d12 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -3487,7 +3487,7 @@ err:
 }
 
 /*
- * Creates a sockpair, a "master-socket" bind conf and a listener. Assigns
+ * Creates a "master-socket" bind conf and a listener. Assigns
  * this new listener to the one "end" of the given process <proc> sockpair in
  * order to have a new master CLI listening socket for this process.
  */
@@ -3498,12 +3498,6 @@ int mworker_cli_global_proxy_new_listener(struct mworker_proc *proc)
 	char *path = NULL;
 	char *err = NULL;
 
-	/* master pipe to ensure the master is still alive  */
-	if (socketpair(AF_UNIX, SOCK_STREAM, 0, proc->ipc_fd) < 0) {
-		ha_alert("Cannot create worker socketpair.\n");
-		return -1;
-	}
-
 	/* XXX: we might want to use a separate frontend at some point */
 	if (!global.cli_fe) {
 		if ((global.cli_fe = cli_alloc_fe("GLOBAL", "master-socket", 0)) == NULL) {
diff --git a/src/haproxy.c b/src/haproxy.c
index 62e1732925..e20f360527 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -109,6 +109,7 @@
 #include <haproxy/peers.h>
 #include <haproxy/pool.h>
 #include <haproxy/protocol.h>
+#include <haproxy/proto_sockpair.h>
 #include <haproxy/proto_tcp.h>
 #include <haproxy/proxy.h>
 #include <haproxy/regex.h>
@@ -2096,8 +2097,18 @@ static void init(int argc, char **argv)
 		}
 		tmproc->options |= PROC_O_TYPE_WORKER; /* worker */
 
-		if (mworker_cli_global_proxy_new_listener(tmproc) < 0)
+		/* create a sockpair to copy it via fork(), thus it will be in
+		 * master and in worker processes
+		 */
+		if (socketpair(AF_UNIX, SOCK_STREAM, 0, tmproc->ipc_fd) < 0) {
+			ha_alert("Cannot create worker master CLI socketpair.\n");
+			exit(EXIT_FAILURE);
+		}
+		if (mworker_cli_global_proxy_new_listener(tmproc) < 0) {
+			close(tmproc->ipc_fd[0]);
+			close(tmproc->ipc_fd[1]);
 			exit(EXIT_FAILURE);
+		}
 
 		LIST_APPEND(&proc_list, &tmproc->list);
 	}