Commit 12b16dad authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent cb8f4048

net/core/filter.c

+44 −28
Original line number Diff line number Diff line
@@ -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 */
@@ -107,12 +118,8 @@ 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);

}

}



/**

 *	sk_filter - run a packet through a socket filter
@@ -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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