Commit de1389b1 authored by Gao feng's avatar Gao feng Committed by Pablo Neira Ayuso
Browse files

netfilter: xt_TCPMSS: Get mtu only if clamp-mss-to-pmtu is specified 



This patch refactors the code to skip tcpmss_reverse_mtu if no
clamp-mss-to-pmtu is specified.

Signed-off-by: default avatarGao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent b21613ae

net/netfilter/xt_TCPMSS.c

+36 −34
Original line number Diff line number Diff line
@@ -43,10 +43,41 @@ optlen(const u_int8_t *opt, unsigned int offset) 
		return opt[offset+1];

}



static u_int32_t tcpmss_reverse_mtu(const struct sk_buff *skb,

				    unsigned int family)

{

	struct flowi fl;

	const struct nf_afinfo *ai;

	struct rtable *rt = NULL;

	u_int32_t mtu     = ~0U;



	if (family == PF_INET) {

		struct flowi4 *fl4 = &fl.u.ip4;

		memset(fl4, 0, sizeof(*fl4));

		fl4->daddr = ip_hdr(skb)->saddr;

	} else {

		struct flowi6 *fl6 = &fl.u.ip6;



		memset(fl6, 0, sizeof(*fl6));

		fl6->daddr = ipv6_hdr(skb)->saddr;

	}

	rcu_read_lock();

	ai = nf_get_afinfo(family);

	if (ai != NULL)

		ai->route(&init_net, (struct dst_entry **)&rt, &fl, false);

	rcu_read_unlock();



	if (rt != NULL) {

		mtu = dst_mtu(&rt->dst);

		dst_release(&rt->dst);

	}

	return mtu;

}



static int

tcpmss_mangle_packet(struct sk_buff *skb,

		     const struct xt_action_param *par,

		     unsigned int in_mtu,

		     unsigned int family,

		     unsigned int tcphoff,

		     unsigned int minlen)

{
@@ -76,6 +107,8 @@ tcpmss_mangle_packet(struct sk_buff *skb, 
		return -1;



	if (info->mss == XT_TCPMSS_CLAMP_PMTU) {

		unsigned int in_mtu = tcpmss_reverse_mtu(skb, family);



		if (dst_mtu(skb_dst(skb)) <= minlen) {

			net_err_ratelimited("unknown or invalid path-MTU (%u)\n",

					    dst_mtu(skb_dst(skb)));
@@ -165,37 +198,6 @@ tcpmss_mangle_packet(struct sk_buff *skb, 
	return TCPOLEN_MSS;

}



static u_int32_t tcpmss_reverse_mtu(const struct sk_buff *skb,

				    unsigned int family)

{

	struct flowi fl;

	const struct nf_afinfo *ai;

	struct rtable *rt = NULL;

	u_int32_t mtu     = ~0U;



	if (family == PF_INET) {

		struct flowi4 *fl4 = &fl.u.ip4;

		memset(fl4, 0, sizeof(*fl4));

		fl4->daddr = ip_hdr(skb)->saddr;

	} else {

		struct flowi6 *fl6 = &fl.u.ip6;



		memset(fl6, 0, sizeof(*fl6));

		fl6->daddr = ipv6_hdr(skb)->saddr;

	}

	rcu_read_lock();

	ai = nf_get_afinfo(family);

	if (ai != NULL)

		ai->route(&init_net, (struct dst_entry **)&rt, &fl, false);

	rcu_read_unlock();



	if (rt != NULL) {

		mtu = dst_mtu(&rt->dst);

		dst_release(&rt->dst);

	}

	return mtu;

}



static unsigned int

tcpmss_tg4(struct sk_buff *skb, const struct xt_action_param *par)

{
@@ -204,7 +206,7 @@ tcpmss_tg4(struct sk_buff *skb, const struct xt_action_param *par) 
	int ret;



	ret = tcpmss_mangle_packet(skb, par,

				   tcpmss_reverse_mtu(skb, PF_INET),

				   PF_INET,

				   iph->ihl * 4,

				   sizeof(*iph) + sizeof(struct tcphdr));

	if (ret < 0)
@@ -233,7 +235,7 @@ tcpmss_tg6(struct sk_buff *skb, const struct xt_action_param *par) 
	if (tcphoff < 0)

		return NF_DROP;

	ret = tcpmss_mangle_packet(skb, par,

				   tcpmss_reverse_mtu(skb, PF_INET6),

				   PF_INET6,

				   tcphoff,

				   sizeof(*ipv6h) + sizeof(struct tcphdr));

	if (ret < 0)