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Date: Thu, 16 Dec 2010 06:45:28 +0100
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next-2.6] 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@...il.com>
---
net/core/filter.c | 72 ++++++++++++++++++++++++++------------------
1 file changed, 44 insertions(+), 28 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index e8a6ac4..2b27d4e 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -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;
}
--
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