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net: filter: add vlan tag access 

BPF filters lack ability to access skb->vlan_tci

This patch adds two new ancillary accessors :

SKF_AD_VLAN_TAG         (44) mapped to vlan_tx_tag_get(skb)

SKF_AD_VLAN_TAG_PRESENT (48) mapped to vlan_tx_tag_present(skb)

This allows libpcap/tcpdump to use a kernel filter instead of
having to fallback to accept all packets, then filter them in
user space.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Ani Sinha <ani@aristanetworks.com>
Suggested-by: Daniel Borkmann <danborkmann@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-10-27 02:26:17 +00:00 committed by David S. Miller
parent 0f6ae8f14e
commit f3335031b9
3 changed files with 14 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/filter.h
View File

@ -123,6 +123,8 @@ enum {
BPF_S_ANC_CPU,
BPF_S_ANC_ALU_XOR_X,
BPF_S_ANC_SECCOMP_LD_W,
BPF_S_ANC_VLAN_TAG,
BPF_S_ANC_VLAN_TAG_PRESENT,
};
#endif /* __LINUX_FILTER_H__ */

4
include/uapi/linux/filter.h
View File

@ -127,7 +127,9 @@ struct sock_fprog { /* Required for SO_ATTACH_FILTER. */
#define SKF_AD_RXHASH 32
#define SKF_AD_CPU 36
#define SKF_AD_ALU_XOR_X 40
#define SKF_AD_MAX 44
#define SKF_AD_VLAN_TAG 44
#define SKF_AD_VLAN_TAG_PRESENT 48
#define SKF_AD_MAX 52
#define SKF_NET_OFF (-0x100000)
#define SKF_LL_OFF (-0x200000)

9
net/core/filter.c
View File

@ -39,6 +39,7 @@
#include <linux/reciprocal_div.h>
#include <linux/ratelimit.h>
#include <linux/seccomp.h>
#include <linux/if_vlan.h>
/* No hurry in this branch
*
@ -341,6 +342,12 @@ load_b:
case BPF_S_ANC_CPU:
A = raw_smp_processor_id();
continue;
case BPF_S_ANC_VLAN_TAG:
A = vlan_tx_tag_get(skb);
continue;
case BPF_S_ANC_VLAN_TAG_PRESENT:
A = !!vlan_tx_tag_present(skb);
continue;
case BPF_S_ANC_NLATTR: {
struct nlattr *nla;
@ -600,6 +607,8 @@ int sk_chk_filter(struct sock_filter *filter, unsigned int flen)
ANCILLARY(RXHASH);
ANCILLARY(CPU);
ANCILLARY(ALU_XOR_X);
ANCILLARY(VLAN_TAG);
ANCILLARY(VLAN_TAG_PRESENT);
}
}
ftest->code = code;