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Commit 0744dd00 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: introduce skb_flow_dissect() 



We use at least two flow dissectors in network stack, with known
limitations and code duplication.

Introduce skb_flow_dissect() to factorize this, highly inspired from
existing dissector from __skb_get_rxhash()

Note : We extensively use skb_header_pointer(), this permits us to not
touch skb at all.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent de0396f4

include/net/flow_keys.h

0 → 100644
+15 −0
Original line number Diff line number Diff line 
#ifndef _NET_FLOW_KEYS_H

#define _NET_FLOW_KEYS_H



struct flow_keys {

	__be32 src;

	__be32 dst;

	union {

		__be32 ports;

		__be16 port16[2];

	};

	u8 ip_proto;

};



extern bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow);

#endif

net/core/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -3,7 +3,7 @@ 
#



obj-y := sock.o request_sock.o skbuff.o iovec.o datagram.o stream.o scm.o \

	 gen_stats.o gen_estimator.o net_namespace.o secure_seq.o

	 gen_stats.o gen_estimator.o net_namespace.o secure_seq.o flow_dissector.o



obj-$(CONFIG_SYSCTL) += sysctl_net_core.o

net/core/flow_dissector.c

0 → 100644
+134 −0
Original line number Diff line number Diff line 
#include <linux/skbuff.h>

#include <linux/ip.h>

#include <linux/ipv6.h>

#include <linux/if_vlan.h>

#include <net/ip.h>

#include <linux/if_tunnel.h>

#include <linux/if_pppox.h>

#include <linux/ppp_defs.h>

#include <net/flow_keys.h>





bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)

{

	int poff, nhoff = skb_network_offset(skb);

	u8 ip_proto;

	__be16 proto = skb->protocol;



	memset(flow, 0, sizeof(*flow));



again:

	switch (proto) {

	case __constant_htons(ETH_P_IP): {

		const struct iphdr *iph;

		struct iphdr _iph;

ip:

		iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);

		if (!iph)

			return false;



		if (ip_is_fragment(iph))

			ip_proto = 0;

		else

			ip_proto = iph->protocol;

		flow->src = iph->saddr;

		flow->dst = iph->daddr;

		nhoff += iph->ihl * 4;

		break;

	}

	case __constant_htons(ETH_P_IPV6): {

		const struct ipv6hdr *iph;

		struct ipv6hdr _iph;

ipv6:

		iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);

		if (!iph)

			return false;



		ip_proto = iph->nexthdr;

		flow->src = iph->saddr.s6_addr32[3];

		flow->dst = iph->daddr.s6_addr32[3];

		nhoff += sizeof(struct ipv6hdr);

		break;

	}

	case __constant_htons(ETH_P_8021Q): {

		const struct vlan_hdr *vlan;

		struct vlan_hdr _vlan;



		vlan = skb_header_pointer(skb, nhoff, sizeof(_vlan), &_vlan);

		if (!vlan)

			return false;



		proto = vlan->h_vlan_encapsulated_proto;

		nhoff += sizeof(*vlan);

		goto again;

	}

	case __constant_htons(ETH_P_PPP_SES): {

		struct {

			struct pppoe_hdr hdr;

			__be16 proto;

		} *hdr, _hdr;

		hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);

		if (!hdr)

			return false;

		proto = hdr->proto;

		nhoff += PPPOE_SES_HLEN;

		switch (proto) {

		case __constant_htons(PPP_IP):

			goto ip;

		case __constant_htons(PPP_IPV6):

			goto ipv6;

		default:

			return false;

		}

	}

	default:

		return false;

	}



	switch (ip_proto) {

	case IPPROTO_GRE: {

		struct gre_hdr {

			__be16 flags;

			__be16 proto;

		} *hdr, _hdr;



		hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);

		if (!hdr)

			return false;

		/*

		 * Only look inside GRE if version zero and no

		 * routing

		 */

		if (!(hdr->flags & (GRE_VERSION|GRE_ROUTING))) {

			proto = hdr->proto;

			nhoff += 4;

			if (hdr->flags & GRE_CSUM)

				nhoff += 4;

			if (hdr->flags & GRE_KEY)

				nhoff += 4;

			if (hdr->flags & GRE_SEQ)

				nhoff += 4;

			goto again;

		}

		break;

	}

	case IPPROTO_IPIP:

		goto again;

	default:

		break;

	}



	flow->ip_proto = ip_proto;

	poff = proto_ports_offset(ip_proto);

	if (poff >= 0) {

		__be32 *ports, _ports;



		nhoff += poff;

		ports = skb_header_pointer(skb, nhoff, sizeof(_ports), &_ports);

		if (ports)

			flow->ports = *ports;

	}



	return true;

}

EXPORT_SYMBOL(skb_flow_dissect);