netdev - [PATCH bpf-next] udp, bpf: Ignore connections in reuseport group after BPF sk lookup

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Date:   Sun, 26 Jul 2020 14:02:28 +0200
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org, kernel-team@...udflare.com,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: [PATCH bpf-next] udp, bpf: Ignore connections in reuseport group after BPF sk lookup

When BPF sk lookup invokes reuseport handling for the selected socket, it
should ignore the fact that reuseport group can contain connected UDP
sockets. With BPF sk lookup this is not relevant as we are not scoring
sockets to find the best match, which might be a connected UDP socket.

Fix it by unconditionally accepting the socket selected by reuseport.

This fixes the following two failures reported by test_progs.

  # ./test_progs -t sk_lookup
  ...
  #73/14 UDP IPv4 redir and reuseport with conns:FAIL
  ...
  #73/20 UDP IPv6 redir and reuseport with conns:FAIL
  ...

Fixes: a57066b1a019 ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net")
Cc: David S. Miller <davem@...emloft.net>
Reported-by: Alexei Starovoitov <alexei.starovoitov@...il.com>
Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
---
 net/ipv4/udp.c | 2 +-
 net/ipv6/udp.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 7ce31beccfc2..e88efba07551 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -473,7 +473,7 @@ static struct sock *udp4_lookup_run_bpf(struct net *net,
 		return sk;
 
 	reuse_sk = lookup_reuseport(net, sk, skb, saddr, sport, daddr, hnum);
-	if (reuse_sk && !reuseport_has_conns(sk, false))
+	if (reuse_sk)
 		sk = reuse_sk;
 	return sk;
 }
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index c394e674f486..29d9691359b9 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -208,7 +208,7 @@ static inline struct sock *udp6_lookup_run_bpf(struct net *net,
 		return sk;
 
 	reuse_sk = lookup_reuseport(net, sk, skb, saddr, sport, daddr, hnum);
-	if (reuse_sk && !reuseport_has_conns(sk, false))
+	if (reuse_sk)
 		sk = reuse_sk;
 	return sk;
 }
-- 
2.25.4