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Code Issues Releases Wiki Activity

filter: optimize accesses to ancillary data

Browse source 
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 @@ unsigned int sk_run_filter(const struct sk_buff *skb,
A = get_unaligned_be32(ptr);
continue;
}
break;
return 0;
case BPF_S_LD_H_ABS:
k = K;
load_h:
@ -278,7 +285,7 @@ unsigned int sk_run_filter(const struct sk_buff *skb,
A = get_unaligned_be16(ptr);
continue;
}
break;
return 0;
case BPF_S_LD_B_ABS:
k = K;
load_b:
@ -287,7 +294,7 @@ unsigned int sk_run_filter(const struct sk_buff *skb,
A = *(u8 *)ptr;
continue;
}
break;
return 0;
case BPF_S_LD_W_LEN:
A = skb->len;
continue;
@ -338,45 +345,35 @@ unsigned int sk_run_filter(const struct sk_buff *skb,
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 @@ unsigned int sk_run_filter(const struct sk_buff *skb,
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 @@ unsigned int sk_run_filter(const struct sk_buff *skb,
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;
}