bpfc: filter: add poff ancillary operation

In preparation for [1], add the #poff operation, so that users can
dynamically truncate packets on the payload start offset. This is
useful for several reasons: privacy, speed, ...

Example for bpfc:

  ld #poff
  ret a

  [1] http://thread.gmane.org/gmane.linux.network/262512

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/bpf.h b/bpf.h
index 84cf0b8..07631d6 100644
--- a/bpf.h
+++ b/bpf.h
@@ -131,5 +131,8 @@ static inline void bpf_release(struct sock_fprog *bpf)
 #ifndef SKF_AD_VLAN_TAG_PRESENT
 # define SKF_AD_VLAN_TAG_PRESENT	48
 #endif
+#ifndef SKF_AD_PAY_OFFSET
+# define SKF_AD_PAY_OFFSET		52
+#endif
 
 #endif /* BPF_I_H */