netdev - [PATCH bpf] bpf: Fix IPv6 dport byte order in bpf_sk_lookup

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Message-ID: <20181107213607.2658130-1-rdna@fb.com>
Date:   Wed, 7 Nov 2018 13:36:07 -0800
From:   Andrey Ignatov <rdna@...com>
To:     <netdev@...r.kernel.org>
CC:     Andrey Ignatov <rdna@...com>, <ast@...nel.org>,
        <daniel@...earbox.net>, <joe@...d.net.nz>, <kernel-team@...com>
Subject: [PATCH bpf] bpf: Fix IPv6 dport byte order in bpf_sk_lookup_udp

Lookup functions in sk_lookup have different expectations about byte
order of provided arguments.

Specifically __inet_lookup, __udp4_lib_lookup and __udp6_lib_lookup
expect dport to be in network byte order and do ntohs(dport) internally.

At the same time __inet6_lookup expects dport to be in host byte order
and correspondingly name the argument hnum.

sk_lookup works correctly with __inet_lookup, __udp4_lib_lookup and
__inet6_lookup with regard to dport. But in __udp6_lib_lookup case it
uses host instead of expected network byte order. It makes result
returned by bpf_sk_lookup_udp for IPv6 incorrect.

The patch fixes byte order of dport passed to __udp6_lib_lookup.

Originally sk_lookup properly handled UDPv6, but not TCPv6. 5ef0ae84f02a
fixes TCPv6 but breaks UDPv6.

Fixes: 5ef0ae84f02a ("bpf: Fix IPv6 dport byte-order in bpf_sk_lookup")
Signed-off-by: Andrey Ignatov <rdna@...com>
---
 net/core/filter.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index e521c5ebc7d1..9a1327eb25fa 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4852,18 +4852,17 @@ static struct sock *sk_lookup(struct net *net, struct bpf_sock_tuple *tuple,
 	} else {
 		struct in6_addr *src6 = (struct in6_addr *)&tuple->ipv6.saddr;
 		struct in6_addr *dst6 = (struct in6_addr *)&tuple->ipv6.daddr;
-		u16 hnum = ntohs(tuple->ipv6.dport);
 		int sdif = inet6_sdif(skb);

 		if (proto == IPPROTO_TCP)
 			sk = __inet6_lookup(net, &tcp_hashinfo, skb, 0,
 					    src6, tuple->ipv6.sport,
-					    dst6, hnum,
+					    dst6, ntohs(tuple->ipv6.dport),
 					    dif, sdif, &refcounted);
 		else if (likely(ipv6_bpf_stub))
 			sk = ipv6_bpf_stub->udp6_lib_lookup(net,
 							    src6, tuple->ipv6.sport,
-							    dst6, hnum,
+							    dst6, tuple->ipv6.dport,
 							    dif, sdif,
 							    &udp_table, skb);
 #endif
-- 
2.17.1