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>

Author: davem330

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
  */
-newmss = min(newmss, (u16)536);
+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;
 
 /*