2 files changed, 22 insertions, 9 deletions

diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c
index afaebc766933..7011c71646f0 100644
--- a/net/netfilter/xt_TCPMSS.c
+++ b/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));
diff --git a/net/netfilter/xt_TCPOPTSTRIP.c b/net/netfilter/xt_TCPOPTSTRIP.c
index 1eb1a44bfd3d..b68fa191710f 100644
--- a/net/netfilter/xt_TCPOPTSTRIP.c
+++ b/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;
 
         /*