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Change pfil starvation prevention from fail-open to fail-close.

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We return ENOBUF to indicate the problem, which is an errno that should be
handled well everywhere.

Requested & Submitted by:	green
Silently okay'ed by:		The rest of the firewall gang
MFC after:			3 days
This commit is contained in:
Max Laier 2004-10-08 12:07:20 +00:00
parent 1f6ac570e4
commit 85bba4455a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=136258
2 changed files with 15 additions and 3 deletions
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6
share/man/man9/pfil.9
View File

@ -203,8 +203,12 @@ When a
.Vt pfil_head
is being modified, no traffic is diverted
(to avoid deadlock).
This means that unwanted traffic may flow for a short period
This means that traffic may be dropped unconditionally for a short period
of time.
.Fn pfil_run_hooks
will return
.Dv ENOBUF
to indicate this.
.Sh SEE ALSO
.Xr bpf 4 ,
.Xr bridge 4

12
sys/net/pfil.c
View File

@ -119,8 +119,16 @@ pfil_run_hooks(struct pfil_head *ph, struct mbuf **mp, struct ifnet *ifp,
struct mbuf *m = *mp;
int rv = 0;
if (ph->ph_busy_count == -1 || ph->ph_want_write)
return (0);
/*
* Prevent packet filtering from starving the modification of
* the packet filters. We would prefer a reader/writer locking
* mechanism with guaranteed ordering, though.
*/
if (ph->ph_busy_count == -1 || ph->ph_want_write) {
m_freem(*mp);
*mp = NULL;
return (ENOBUFS);
}
PFIL_RLOCK(ph);
for (pfh = pfil_hook_get(dir, ph); pfh != NULL;