Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf

Pablo Neira Ayuso says:

====================
The following patchset contains Netfilter fixes. They are targeted to the
TCP option targets, that have receive some scrinity in the last week. The
changes are:

* Fix TCPOPTSTRIP, it stopped working in the forward chain as tcp_hdr
  uses skb->transport_header, and we cannot use that in the forwarding
  case, from myself.

* Fix default IPv6 MSS in TCPMSS in case of absence of TCP MSS options,
  from Phil Oester.

* Fix missing fragmentation handling again in TCPMSS, from Phil Oester.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/xt_TCPMSS.c

@@ -45,17 +45,22 @@ optlen(const u_int8_t *opt, unsigned int offset)
 
 static int
 tcpmss_mangle_packet(struct sk_buff *skb,
-		     const struct xt_tcpmss_info *info,
+		     const struct xt_action_param *par,
 		     unsigned int in_mtu,
 		     unsigned int tcphoff,
 		     unsigned int minlen)
 {
+	const struct xt_tcpmss_info *info = par->targinfo;
 	struct tcphdr *tcph;
 	unsigned int tcplen, i;
 	__be16 oldval;
 	u16 newmss;
 	u8 *opt;
 
+	/* This is a fragment, no TCP header is available */
+	if (par->fragoff != 0)
+		return XT_CONTINUE;
+
 	if (!skb_make_writable(skb, skb->len))
 		return -1;
 
@@ -125,11 +130,17 @@ tcpmss_mangle_packet(struct sk_buff *skb,
 
 	skb_put(skb, TCPOLEN_MSS);
 
-	/* RFC 879 states that the default MSS is 536 without specific
-	 * knowledge that the destination host is prepared to accept larger.
-	 * Since no MSS was provided, we MUST NOT set a value > 536.
+	/*
+	 * IPv4: RFC 1122 states "If an MSS option is not received at
+	 * connection setup, TCP MUST assume a default send MSS of 536".
+	 * IPv6: RFC 2460 states IPv6 has a minimum MTU of 1280 and a minimum
+	 * length IPv6 header of 60, ergo the default MSS value is 1220
+	 * Since no MSS was provided, we must use the default values
 	 */
+	if (par->family == NFPROTO_IPV4)
 		newmss = min(newmss, (u16)536);
+	else
+		newmss = min(newmss, (u16)1220);
 
 	opt = (u_int8_t *)tcph + sizeof(struct tcphdr);
 	memmove(opt + TCPOLEN_MSS, opt, tcplen - sizeof(struct tcphdr));
@@ -188,7 +199,7 @@ tcpmss_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 	__be16 newlen;
 	int ret;
 
-	ret = tcpmss_mangle_packet(skb, par->targinfo,
+	ret = tcpmss_mangle_packet(skb, par,
 				   tcpmss_reverse_mtu(skb, PF_INET),
 				   iph->ihl * 4,
 				   sizeof(*iph) + sizeof(struct tcphdr));
@@ -217,7 +228,7 @@ tcpmss_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 	tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr, &frag_off);
 	if (tcphoff < 0)
 		return NF_DROP;
-	ret = tcpmss_mangle_packet(skb, par->targinfo,
+	ret = tcpmss_mangle_packet(skb, par,
 				   tcpmss_reverse_mtu(skb, PF_INET6),
 				   tcphoff,
 				   sizeof(*ipv6h) + sizeof(struct tcphdr));

net/netfilter/xt_TCPOPTSTRIP.c

@@ -48,11 +48,13 @@ tcpoptstrip_mangle_packet(struct sk_buff *skb,
 		return NF_DROP;
 
 	len = skb->len - tcphoff;
-	if (len < (int)sizeof(struct tcphdr) ||
-	    tcp_hdr(skb)->doff * 4 > len)
+	if (len < (int)sizeof(struct tcphdr))
 		return NF_DROP;
 
 	tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
+	if (tcph->doff * 4 > len)
+		return NF_DROP;
+
 	opt  = (u_int8_t *)tcph;
 
 	/*