git: 5050df3f4aa4 - main - tcp: fix counter leak for SYN_RCVD state when syncache_socket() fails

The branch main has been updated by glebius:

URL: https://cgit.FreeBSD.org/src/commit/?id=5050df3f4aa4867ef8ab49e3116ade64442a5f21

commit 5050df3f4aa4867ef8ab49e3116ade64442a5f21
Author:     Gleb Smirnoff <glebius@FreeBSD.org>
AuthorDate: 2022-12-14 03:31:05 +0000
Commit:     Gleb Smirnoff <glebius@FreeBSD.org>
CommitDate: 2022-12-14 03:31:05 +0000

    tcp: fix counter leak for SYN_RCVD state when syncache_socket() fails
    
    The SYN_RCVD state count is tricky here due to default code path and TFO
    being so different.  In the default case the count is incremented when a
    syncache entry is added to the the database in syncache_insert().  Later
    when connection transitions from syncache entry to a socket in
    syncache_expand(), this counter is inherited by the tcpcb.  If socket or
    tcpcb allocation failed in syncache_socket() failed the syncache_expand()
    is responsible for decrement.  In the TFO case the syncache entry is not
    inserted into database and count of SYN_RCVD is first incremented in the
    syncache_tfo_expand() after successful socket allocation.  Thus, inside
    syncache_socket() we can't tell whether we need to decrement in a case of
    a failure or not.  The caller is responsible for this book keeping.
    
    Fixes:  07285bb4c22c026a50f69149d5dae03169b15fe4
    Differential revision:  https://reviews.freebsd.org/D37610
---
 sys/netinet/tcp_syncache.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sys/netinet/tcp_syncache.c b/sys/netinet/tcp_syncache.c
index 00d0ac2fa9d5..1a4cde642d4a 100644
--- a/sys/netinet/tcp_syncache.c
+++ b/sys/netinet/tcp_syncache.c
@@ -1313,9 +1313,10 @@ syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
 
 	*lsop = syncache_socket(sc, *lsop, m);
 
-	if (*lsop == NULL)
+	if (__predict_false(*lsop == NULL)) {
 		TCPSTAT_INC(tcps_sc_aborted);
-	else
+		TCPSTATES_DEC(TCPS_SYN_RECEIVED);
+	} else
 		TCPSTAT_INC(tcps_sc_completed);
 
 /* how do we find the inp for the new socket? */