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filter: optimize accesses to ancillary data 

We can translate pseudo load instructions at filter check time to
dedicated instructions to speed up filtering and avoid one switch().
libpcap currently uses SKF_AD_PROTOCOL, but custom filters probably use
other ancillary accesses.

Note : I made the assertion that ancillary data was always accessed with
BPF_LD|BPF_?|BPF_ABS instructions, not with BPF_LD|BPF_?|BPF_IND ones
(offset given by K constant, not by K + X register)

On x86_64, this saves a few bytes of text :

# size net/core/filter.o.*
   text	   data	    bss	    dec	    hex	filename
   4864	      0	      0	   4864	   1300	net/core/filter.o.new
   4944	      0	      0	   4944	   1350	net/core/filter.o.old

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2010-12-15 19:45:28 +00:00 committed by David S. Miller
parent cb8f404893
commit 12b16dadbc
1 changed files with 44 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

72
net/core/filter.c
View File

@ -85,6 +85,17 @@ enum {
BPF_S_JMP_JGT_X,
BPF_S_JMP_JSET_K,
BPF_S_JMP_JSET_X,
/* Ancillary data */
BPF_S_ANC_PROTOCOL,
BPF_S_ANC_PKTTYPE,
BPF_S_ANC_IFINDEX,
BPF_S_ANC_NLATTR,
BPF_S_ANC_NLATTR_NEST,
BPF_S_ANC_MARK,
BPF_S_ANC_QUEUE,
BPF_S_ANC_HATYPE,
BPF_S_ANC_RXHASH,
BPF_S_ANC_CPU,
};
/* No hurry in this branch */
@ -107,11 +118,7 @@ static inline void *load_pointer(const struct sk_buff *skb, int k,
{
if (k >= 0)
return skb_header_pointer(skb, k, size, buffer);
else {
if (k >= SKF_AD_OFF)
return NULL;
return __load_pointer(skb, k, size);
}
return __load_pointer(skb, k, size);
}
/**
@ -269,7 +276,7 @@ load_w:
A = get_unaligned_be32(ptr);
continue;
}
break;
return 0;
case BPF_S_LD_H_ABS:
k = K;
load_h:
@ -278,7 +285,7 @@ load_h:
A = get_unaligned_be16(ptr);
continue;
}
break;
return 0;
case BPF_S_LD_B_ABS:
k = K;
load_b:
@ -287,7 +294,7 @@ load_b:
A = *(u8 *)ptr;
continue;
}
break;
return 0;
case BPF_S_LD_W_LEN:
A = skb->len;
continue;
@ -338,45 +345,35 @@ load_b:
case BPF_S_STX:
mem[K] = X;
continue;
default:
WARN_ON(1);
return 0;
}
/*
* Handle ancillary data, which are impossible
* (or very difficult) to get parsing packet contents.
*/
switch (k-SKF_AD_OFF) {
case SKF_AD_PROTOCOL:
case BPF_S_ANC_PROTOCOL:
A = ntohs(skb->protocol);
continue;
case SKF_AD_PKTTYPE:
case BPF_S_ANC_PKTTYPE:
A = skb->pkt_type;
continue;
case SKF_AD_IFINDEX:
case BPF_S_ANC_IFINDEX:
if (!skb->dev)
return 0;
A = skb->dev->ifindex;
continue;
case SKF_AD_MARK:
case BPF_S_ANC_MARK:
A = skb->mark;
continue;
case SKF_AD_QUEUE:
case BPF_S_ANC_QUEUE:
A = skb->queue_mapping;
continue;
case SKF_AD_HATYPE:
case BPF_S_ANC_HATYPE:
if (!skb->dev)
return 0;
A = skb->dev->type;
continue;
case SKF_AD_RXHASH:
case BPF_S_ANC_RXHASH:
A = skb->rxhash;
continue;
case SKF_AD_CPU:
case BPF_S_ANC_CPU:
A = raw_smp_processor_id();
continue;
case SKF_AD_NLATTR: {
case BPF_S_ANC_NLATTR: {
struct nlattr *nla;
if (skb_is_nonlinear(skb))
@ -392,7 +389,7 @@ load_b:
A = 0;
continue;
}
case SKF_AD_NLATTR_NEST: {
case BPF_S_ANC_NLATTR_NEST: {
struct nlattr *nla;
if (skb_is_nonlinear(skb))
@ -412,6 +409,7 @@ load_b:
continue;
}
default:
WARN_ON(1);
return 0;
}
}
@ -600,6 +598,24 @@ int sk_chk_filter(struct sock_filter *filter, int flen)
pc + ftest->jf + 1 >= flen)
return -EINVAL;
break;
case BPF_S_LD_W_ABS:
case BPF_S_LD_H_ABS:
case BPF_S_LD_B_ABS:
#define ANCILLARY(CODE) case SKF_AD_OFF + SKF_AD_##CODE: \
code = BPF_S_ANC_##CODE; \
break
switch (ftest->k) {
ANCILLARY(PROTOCOL);
ANCILLARY(PKTTYPE);
ANCILLARY(IFINDEX);
ANCILLARY(NLATTR);
ANCILLARY(NLATTR_NEST);
ANCILLARY(MARK);
ANCILLARY(QUEUE);
ANCILLARY(HATYPE);
ANCILLARY(RXHASH);
ANCILLARY(CPU);
}
}
ftest->code = code;
}