Author: melifaro
Date: Wed Jun 11 11:27:44 2014
New Revision: 267361
URL: http://svnweb.freebsd.org/changeset/base/267361
Log:
Improve logic besides net.bpf.optimize_writers.
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
Modified:
head/sys/net/bpf.c
Modified: head/sys/net/bpf.c
==============================================================================
--- head/sys/net/bpf.c Wed Jun 11 10:48:11 2014 (r267360)
+++ head/sys/net/bpf.c Wed Jun 11 11:27:44 2014 (r267361)
@@ -643,6 +643,67 @@ bpf_attachd(struct bpf_d *d, struct bpf_
}
/*
+ * 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_pro
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_pro
#endif
/* Move d to active readers list. */
- if (need_upgrade)
+ if (need_upgrade != 0)
bpf_upgraded(d);
BPF_UNLOCK();
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