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Commit d64d80a2 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by Pablo Neira Ayuso
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netfilter: x_tables: don't extract flow keys on early demuxed sks in socket match 



Currently in xt_socket, we take advantage of early demuxed sockets
since commit 00028aa3 ("netfilter: xt_socket: use IP early demux")
in order to avoid a second socket lookup in the fast path, but we
only make partial use of this:

We still unnecessarily parse headers, extract proto, {s,d}addr and
{s,d}ports from the skb data, accessing possible conntrack information,
etc even though we were not even calling into the socket lookup via
xt_socket_get_sock_{v4,v6}() due to skb->sk hit, meaning those cycles
can be spared.

After this patch, we only proceed the slower, manual lookup path
when we have a skb->sk miss, thus time to match verdict for early
demuxed sockets will improve further, which might be i.e. interesting
for use cases such as mentioned in 681f130f ("netfilter: xt_socket:
add XT_SOCKET_NOWILDCARD flag").

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 0b67c43c

net/netfilter/xt_socket.c

+50 −45
Original line number Diff line number Diff line
@@ -143,13 +143,10 @@ static bool xt_socket_sk_is_transparent(struct sock *sk) 
	}

}



static bool

socket_match(const struct sk_buff *skb, struct xt_action_param *par,

	     const struct xt_socket_mtinfo1 *info)

static struct sock *xt_socket_lookup_slow_v4(const struct sk_buff *skb,

					     const struct net_device *indev)

{

	const struct iphdr *iph = ip_hdr(skb);

	struct udphdr _hdr, *hp = NULL;

	struct sock *sk = skb->sk;

	__be32 uninitialized_var(daddr), uninitialized_var(saddr);

	__be16 uninitialized_var(dport), uninitialized_var(sport);

	u8 uninitialized_var(protocol);
@@ -159,10 +156,12 @@ socket_match(const struct sk_buff *skb, struct xt_action_param *par, 
#endif



	if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {

		struct udphdr _hdr, *hp;



		hp = skb_header_pointer(skb, ip_hdrlen(skb),

					sizeof(_hdr), &_hdr);

		if (hp == NULL)

			return false;

			return NULL;



		protocol = iph->protocol;

		saddr = iph->saddr;
@@ -173,15 +172,16 @@ socket_match(const struct sk_buff *skb, struct xt_action_param *par, 
	} else if (iph->protocol == IPPROTO_ICMP) {

		if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,

					 &sport, &dport))

			return false;

			return NULL;

	} else {

		return false;

		return NULL;

	}



#ifdef XT_SOCKET_HAVE_CONNTRACK

	/* Do the lookup with the original socket address in case this is a

	 * reply packet of an established SNAT-ted connection. */



	/* Do the lookup with the original socket address in

	 * case this is a reply packet of an established

	 * SNAT-ted connection.

	 */

	ct = nf_ct_get(skb, &ctinfo);

	if (ct && !nf_ct_is_untracked(ct) &&

	    ((iph->protocol != IPPROTO_ICMP &&
@@ -197,10 +197,18 @@ socket_match(const struct sk_buff *skb, struct xt_action_param *par, 
	}

#endif



	return xt_socket_get_sock_v4(dev_net(skb->dev), protocol, saddr, daddr,

				     sport, dport, indev);

}



static bool

socket_match(const struct sk_buff *skb, struct xt_action_param *par,

	     const struct xt_socket_mtinfo1 *info)

{

	struct sock *sk = skb->sk;



	if (!sk)

		sk = xt_socket_get_sock_v4(dev_net(skb->dev), protocol,

					   saddr, daddr, sport, dport,

					   par->in);

		sk = xt_socket_lookup_slow_v4(skb, par->in);

	if (sk) {

		bool wildcard;

		bool transparent = true;
@@ -225,12 +233,7 @@ socket_match(const struct sk_buff *skb, struct xt_action_param *par, 
			sk = NULL;

	}



	pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",

		 protocol, &saddr, ntohs(sport),

		 &daddr, ntohs(dport),

		 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);



	return (sk != NULL);

	return sk != NULL;

}



static bool
@@ -327,28 +330,26 @@ xt_socket_get_sock_v6(struct net *net, const u8 protocol, 
	return NULL;

}



static bool

socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)

static struct sock *xt_socket_lookup_slow_v6(const struct sk_buff *skb,

					     const struct net_device *indev)

{

	struct ipv6hdr ipv6_var, *iph = ipv6_hdr(skb);

	struct udphdr _hdr, *hp = NULL;

	struct sock *sk = skb->sk;

	const struct in6_addr *daddr = NULL, *saddr = NULL;

	__be16 uninitialized_var(dport), uninitialized_var(sport);

	int thoff = 0, uninitialized_var(tproto);

	const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;

	const struct in6_addr *daddr = NULL, *saddr = NULL;

	struct ipv6hdr *iph = ipv6_hdr(skb);

	int thoff = 0, tproto;



	tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);

	if (tproto < 0) {

		pr_debug("unable to find transport header in IPv6 packet, dropping\n");

		return NF_DROP;

		return NULL;

	}



	if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {

		hp = skb_header_pointer(skb, thoff,

					sizeof(_hdr), &_hdr);

		struct udphdr _hdr, *hp;



		hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);

		if (hp == NULL)

			return false;

			return NULL;



		saddr = &iph->saddr;

		sport = hp->source;
@@ -356,17 +357,27 @@ socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par) 
		dport = hp->dest;



	} else if (tproto == IPPROTO_ICMPV6) {

		struct ipv6hdr ipv6_var;



		if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,

					 &sport, &dport, &ipv6_var))

			return false;

			return NULL;

	} else {

		return false;

		return NULL;

	}



	return xt_socket_get_sock_v6(dev_net(skb->dev), tproto, saddr, daddr,

				     sport, dport, indev);

}



static bool

socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)

{

	const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;

	struct sock *sk = skb->sk;



	if (!sk)

		sk = xt_socket_get_sock_v6(dev_net(skb->dev), tproto,

					   saddr, daddr, sport, dport,

					   par->in);

		sk = xt_socket_lookup_slow_v6(skb, par->in);

	if (sk) {

		bool wildcard;

		bool transparent = true;
@@ -391,13 +402,7 @@ socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par) 
			sk = NULL;

	}



	pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "

		 "(orig %pI6:%hu) sock %p\n",

		 tproto, saddr, ntohs(sport),

		 daddr, ntohs(dport),

		 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);



	return (sk != NULL);

	return sk != NULL;

}

#endif