soreuseport: TCP/IPv4 implementation
Allow multiple listener sockets to bind to the same port.
Motivation for soresuseport would be something like a web server
binding to port 80 running with multiple threads, where each thread
might have it's own listener socket. This could be done as an
alternative to other models: 1) have one listener thread which
dispatches completed connections to workers. 2) accept on a single
listener socket from multiple threads. In case #1 the listener thread
can easily become the bottleneck with high connection turn-over rate.
In case #2, the proportion of connections accepted per thread tends
to be uneven under high connection load (assuming simple event loop:
while (1) { accept(); process() }, wakeup does not promote fairness
among the sockets. We have seen the disproportion to be as high
as 3:1 ratio between thread accepting most connections and the one
accepting the fewest. With so_reusport the distribution is
uniform.
Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index c6ce9ca..bbbdcc5 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -657,7 +657,8 @@
* no RST generated if md5 hash doesn't match.
*/
sk1 = __inet_lookup_listener(dev_net(skb_dst(skb)->dev),
- &tcp_hashinfo, ip_hdr(skb)->daddr,
+ &tcp_hashinfo, ip_hdr(skb)->saddr,
+ th->source, ip_hdr(skb)->daddr,
ntohs(th->source), inet_iif(skb));
/* don't send rst if it can't find key */
if (!sk1)
@@ -2074,6 +2075,7 @@
case TCP_TW_SYN: {
struct sock *sk2 = inet_lookup_listener(dev_net(skb->dev),
&tcp_hashinfo,
+ iph->saddr, th->source,
iph->daddr, th->dest,
inet_iif(skb));
if (sk2) {