fix reuseaddr regression

I introduced a regression when reworking the fastreuse port stuff that allows bind conflicts to occur once a reuseaddr socket successfully opens on an existing tb. The root cause is I reversed an if statement which caused us to set the tb as if there were no owners on the socket if there were, which obviously is not correct.

Dave I have follow up patches that will add a selftest for this case and I ran the other reuseport related tests as well. These need to go in pretty quickly as it breaks kvm, I've marked them for stable. Sorry for the regression,

Josef

From: Josef Bacik <[email protected]>

We need to set the tb->fast_sk_family properly so we can use the proper comparison function for all subsequent reuseport bind requests.

---
 net/ipv4/inet_connection_sock.c | 2 ++
 1 file changed, 2 insertions(+)

index b9c64b40a83a..f87f4805e244 100644
@@ -328,6 +328,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 			tb->fastuid = uid;
 			tb->fast_rcv_saddr = sk->sk_rcv_saddr;
 			tb->fast_ipv6_only = ipv6_only_sock(sk);
+			tb->fast_sk_family = sk->sk_family;
 #if IS_ENABLED(CONFIG_IPV6)
 			tb->fast_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
 #endif

@@ -354,6 +355,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 				tb->fastuid = uid;
 				tb->fast_rcv_saddr = sk->sk_rcv_saddr;
 				tb->fast_ipv6_only = ipv6_only_sock(sk);
+				tb->fast_sk_family = sk->sk_family;
 #if IS_ENABLED(CONFIG_IPV6)
 				tb->fast_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
 #endif

2.7.4

From: Josef Bacik <[email protected]>

In ipv6_rcv_saddr_equal() we need to use inet6_rcv_saddr(sk) for the ipv6 compare with the fast socket information to make sure we're doing the proper comparisons.

---
 net/ipv4/inet_connection_sock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index f87f4805e244..a1bf30438bc5 100644
@@ -266,7 +266,7 @@ static inline int sk_reuseport_match(struct inet_bind_bucket *tb,
 #if IS_ENABLED(CONFIG_IPV6)
 	if (tb->fast_sk_family == AF_INET6)
 		return ipv6_rcv_saddr_equal(&tb->fast_v6_rcv_saddr,
-					    &sk->sk_v6_rcv_saddr,
+					    inet6_rcv_saddr(sk),
 					    tb->fast_rcv_saddr,
 					    sk->sk_rcv_saddr,
 					    tb->fast_ipv6_only,

2.7.4

From: Josef Bacik <[email protected]>

When doing my reuseport rework I screwed up and changed a

if (hlist_empty(&tb->owners))

to

if (!hlist_empty(&tb->owners))

This is obviously bad as all of the reuseport/reuse logic was reversed, which caused weird problems like allowing an ipv4 bind conflict if we opened an ipv4 only socket on a port followed by an ipv6 only socket on the same port.

---
 net/ipv4/inet_connection_sock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index a1bf30438bc5..c039c937ba90 100644
@@ -321,7 +321,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 			goto fail_unlock;
 	}
 success:
-	if (!hlist_empty(&tb->owners)) {
+	if (hlist_empty(&tb->owners)) {
 		tb->fastreuse = reuse;
 		if (sk->sk_reuseport) {
 			tb->fastreuseport = FASTREUSEPORT_ANY;

2.7.4

To clarify, it doesn't really break KVM specifically, but it breaks a port collision detection idiom that libvirt depends on to successfully launch qemu/xen/... VMs in certain cases.

Thanks,
Cole

From: [email protected]
Date: Mon, 18 Sep 2017 12:28:54 -0400

First, please fix your "From: " field so that it actually has your full name rather than just your email address. This matter when I apply your patches.

Second, remove the stable CC:. For networking changes, you simply ask me to queue the changes up for -stable.

Thanks.

Sorry Dave, I've fixed my git email settings and I droped the stable cc and sent a new round. Didn't see this until just now, my bad.

Josef