git: 814fc45f3154 - stable/15 - tcp: Enable symmetric hashing by setting hash on outgoing conns

The branch stable/15 has been updated by kbowling:

URL: https://cgit.FreeBSD.org/src/commit/?id=814fc45f3154d3a2442681fdec41e26d43beb7b6

commit 814fc45f3154d3a2442681fdec41e26d43beb7b6
Author:     Andrew Gallatin <gallatin@FreeBSD.org>
AuthorDate: 2025-11-22 14:29:35 +0000
Commit:     Kevin Bowling <kbowling@FreeBSD.org>
CommitDate: 2026-10-29 07:37:57 +0000

    tcp: Enable symmetric hashing by setting hash on outgoing conns
    
    Now that we can trust NICs to supply an identical hash result
    to software, we can setup the inpcb hash on outgoing connections.
    This gives us symmetric hashing, meaning packets should enter
    and leave on the same NIC queue.
    
    Differential Revision:  https://reviews.freebsd.org/D53104
    Reviewed by: adrian, cc, kbowling, tuexen, zlei
    Sponsored by: Netflix
    
    (cherry picked from commit dd0e6bb996dc46e1d91f3d9aef87979716479465)
---
 sys/netinet/tcp_usrreq.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sys/netinet/tcp_usrreq.c b/sys/netinet/tcp_usrreq.c
index 6b2388b9363c..9423a54a8a31 100644
--- a/sys/netinet/tcp_usrreq.c
+++ b/sys/netinet/tcp_usrreq.c
@@ -75,6 +75,7 @@
 #include <netinet/in.h>
 #include <netinet/in_kdtrace.h>
 #include <netinet/in_pcb.h>
+#include <netinet/in_rss.h>
 #include <netinet/in_systm.h>
 #include <netinet/in_var.h>
 #include <netinet/ip.h>
@@ -82,6 +83,7 @@
 #ifdef INET6
 #include <netinet/ip6.h>
 #include <netinet6/in6_pcb.h>
+#include <netinet6/in6_rss.h>
 #include <netinet6/ip6_var.h>
 #include <netinet6/scope6_var.h>
 #endif
@@ -1488,6 +1490,10 @@ tcp_connect(struct tcpcb *tp, struct sockaddr_in *sin, struct thread *td)
 	if (error != 0)
 		return (error);
 
+	/* set the hash on the connection */
+	rss_proto_software_hash_v4(inp->inp_faddr, inp->inp_laddr,
+	    inp->inp_fport, inp->inp_lport, IPPROTO_TCP,
+	    &inp->inp_flowid, &inp->inp_flowtype);
 	/*
 	 * Compute window scaling to request:
 	 * Scale to fit into sweet spot.  See tcp_syncache.c.
@@ -1533,6 +1539,10 @@ tcp6_connect(struct tcpcb *tp, struct sockaddr_in6 *sin6, struct thread *td)
 	if (error != 0)
 		return (error);
 
+	/* set the hash on the connection */
+	rss_proto_software_hash_v6(&inp->in6p_faddr,
+	    &inp->in6p_laddr, inp->inp_fport, inp->inp_lport, IPPROTO_TCP,
+	    &inp->inp_flowid, &inp->inp_flowtype);
 	/* Compute window scaling to request.  */
 	while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
 	    (TCP_MAXWIN << tp->request_r_scale) < sb_max)