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authorLorenzo Colitti <lorenzo@google.com>2018-10-29 09:15:22 +0900
committerDavid S. Miller <davem@davemloft.net>2018-10-28 19:27:21 -0700
commit747569b0a7c537d680bc94a988be6caad9960488 (patch)
treea1537a109e82873ad423a4f836457ebc426f0990 /net
parent3bdf6bac58170383465a2fb67cf6e13a27e43b85 (diff)
downloadlinux-747569b0a7c537d680bc94a988be6caad9960488.tar.gz
net: diag: document swapped src/dst in udp_dump_one.
Since its inception, udp_dump_one has had a bug where userspace needs to swap src and dst addresses and ports in order to find the socket it wants. This is because it passes the socket source address to __udp[46]_lib_lookup's saddr argument, but those functions are intended to find local sockets matching received packets, so saddr is the remote address, not the local address. This can no longer be fixed for backwards compatibility reasons, so add a brief comment explaining that this is the case. This will avoid confusion and help ensure SOCK_DIAG implementations of new protocols don't have the same problem. Fixes: a925aa00a55 ("udp_diag: Implement the get_exact dumping functionality") Signed-off-by: Lorenzo Colitti <lorenzo@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/udp_diag.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/ipv4/udp_diag.c b/net/ipv4/udp_diag.c
index d9ad986c7b2c..5cbb9be05295 100644
--- a/net/ipv4/udp_diag.c
+++ b/net/ipv4/udp_diag.c
@@ -42,6 +42,7 @@ static int udp_dump_one(struct udp_table *tbl, struct sk_buff *in_skb,
rcu_read_lock();
if (req->sdiag_family == AF_INET)
+ /* src and dst are swapped for historical reasons */
sk = __udp4_lib_lookup(net,
req->id.idiag_src[0], req->id.idiag_sport,
req->id.idiag_dst[0], req->id.idiag_dport,