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Improve logic besides net.bpf.optimize_writers.

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Direct bpf(4) consumers should now work fine with this tunable turned on.
In fact, the only case when optimized_writers can change program
behavior is direct bpf(4) consumer setting its read filter to
catch-all one.

MFC after:	2 weeks
Sponsored by:	Yandex LLC
This commit is contained in:
Alexander V. Chernikov 2014-06-11 11:27:44 +00:00
parent d68d0cf5d9
commit 402000ffa3
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=267361
1 changed files with 63 additions and 12 deletions
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75
sys/net/bpf.c
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@ -642,6 +642,67 @@ bpf_attachd(struct bpf_d *d, struct bpf_if *bp)
EVENTHANDLER_INVOKE(bpf_track, bp->bif_ifp, bp->bif_dlt, 1);
}
/*
* Check if we need to upgrade our descriptor @d from write-only mode.
*/
static int
bpf_check_upgrade(u_long cmd, struct bpf_d *d, struct bpf_insn *fcode, int flen)
{
int is_snap, need_upgrade;
/*
* Check if we've already upgraded or new filter is empty.
*/
if (d->bd_writer == 0 || fcode == NULL)
return (0);
need_upgrade = 0;
/*
* Check if cmd looks like snaplen setting from
* pcap_bpf.c:pcap_open_live().
* Note we're not checking .k value here:
* while pcap_open_live() definitely sets to to non-zero value,
* we'd prefer to treat k=0 (deny ALL) case the same way: e.g.
* do not consider upgrading immediately
*/
if (cmd == BIOCSETF && flen == 1 && fcode[0].code == (BPF_RET | BPF_K))
is_snap = 1;
else
is_snap = 0;
if (is_snap == 0) {
/*
* We're setting first filter and it doesn't look like
* setting snaplen. We're probably using bpf directly.
* Upgrade immediately.
*/
need_upgrade = 1;
} else {
/*
* Do not require upgrade by first BIOCSETF
* (used to set snaplen) by pcap_open_live().
*/
if (--d->bd_writer == 0) {
/*
* First snaplen filter has already
* been set. This is probably catch-all
* filter
*/
need_upgrade = 1;
}
}
CTR5(KTR_NET,
"%s: filter function set by pid %d, "
"bd_writer counter %d, snap %d upgrade %d",
__func__, d->bd_pid, d->bd_writer,
is_snap, need_upgrade);
return (need_upgrade);
}
/*
* Add d to the list of active bp filters.
* Reuqires bpf_attachd() to be called before
@ -1802,17 +1863,7 @@ bpf_setf(struct bpf_d *d, struct bpf_program *fp, u_long cmd)
if (cmd == BIOCSETF)
reset_d(d);
if (fcode != NULL) {
/*
* Do not require upgrade by first BIOCSETF
* (used to set snaplen) by pcap_open_live().
*/
if (d->bd_writer != 0 && --d->bd_writer == 0)
need_upgrade = 1;
CTR4(KTR_NET, "%s: filter function set by pid %d, "
"bd_writer counter %d, need_upgrade %d",
__func__, d->bd_pid, d->bd_writer, need_upgrade);
}
need_upgrade = bpf_check_upgrade(cmd, d, fcode, flen);
}
BPFD_UNLOCK(d);
if (d->bd_bif != NULL)
@ -1825,7 +1876,7 @@ bpf_setf(struct bpf_d *d, struct bpf_program *fp, u_long cmd)
#endif
/* Move d to active readers list. */
if (need_upgrade)
if (need_upgrade != 0)
bpf_upgraded(d);
BPF_UNLOCK();