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Fix implicit automatic local port selection for IPv6 during connect calls.

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When a user creates a TCP socket and tries to connect to the socket without
explicitly binding the socket to a local address, the connect call
implicitly chooses an appropriate local port. When evaluating candidate
local ports, the algorithm checks for conflicts with existing ports by
doing a lookup in the connection hash table.

In this circumstance, both the IPv4 and IPv6 code look for exact matches
in the hash table. However, the IPv4 code goes a step further and checks
whether the proposed 4-tuple will match wildcard (e.g. TCP "listen")
entries. The IPv6 code has no such check.

The missing wildcard check can cause problems when connecting to a local
server. It is possible that the algorithm will choose the same value for
the local port as the foreign port uses. This results in a connection with
identical source and destination addresses and ports. Changing the IPv6
code to align with the IPv4 code's behavior fixes this problem.

Reviewed by:	tuexen
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D27164
This commit is contained in:
Jonathan T. Looney 2020-11-14 14:50:34 +00:00
parent 32f4592764
commit 440598dd9e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=367680
1 changed files with 2 additions and 1 deletions
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3
sys/netinet6/in6_pcb.c
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@ -464,7 +464,8 @@ in6_pcbconnect_mbuf(struct inpcb *inp, struct sockaddr *nam,
rehash = false;
error = in_pcb_lport_dest(inp,
(struct sockaddr *) &laddr6, &inp->inp_lport,
(struct sockaddr *) sin6, sin6->sin6_port, cred, 0);
(struct sockaddr *) sin6, sin6->sin6_port, cred,
INPLOOKUP_WILDCARD);
if (error)
return (error);
}