On Wed, Apr 06, 2016 at 01:27:11PM -0400, Willem de Bruijn wrote: > On Wed, Apr 6, 2016 at 12:54 PM, Weongyo Jeong <weongyo.li...@gmail.com> > wrote: > > consume_skb() isn't for drop or error cases. kfree_skb() is more proper > > one. > > Signed-off-by: Weongyo Jeong <weongyo.li...@gmail.com> > > --- > > net/packet/af_packet.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c > > index 1ecfa71..a75d5bf 100644 > > --- a/net/packet/af_packet.c > > +++ b/net/packet/af_packet.c > > @@ -2141,7 +2141,7 @@ drop_n_restore: > > skb->len = skb_len; > > } > > drop: > > - consume_skb(skb); > > + kfree_skb(skb); > > This does show an inconsistency between packet_rcv and tpacket_rcv, > which calls kfree_skb. > > A comment at consume_skb mentions that kfree_skb is intended for drops > that signal a failure condition, and indeed, that makes it a useful > way to track errors (e.g., with perf record -a -g -e skb:kfree_skb). > > This drop path is not always an error path, though. These network taps > will legitimately drop references to any packets not destined to them. > To be precise, only the drop_n_acct label cases are delivery errors > (drops after the filter accepted the packet). Changing unconditionally > to kfree_skb does pollute that useful counter with false positives. A > pedantic solution is to change both functions to only call kfree_skb > on drop_n_acct and consume_skb otherwise. > > This shorthand change does at least makes packet_rcv and tpacket_rcv more > alike.
Thank you for comments. I'll try to submit patch v2 for this case. Regards, Weongyo Jeong
