diff options
| -rw-r--r-- | net/netfilter/xt_TCPMSS.c | 25 | ||||
| -rw-r--r-- | net/netfilter/xt_TCPOPTSTRIP.c | 6 |
2 files changed, 22 insertions, 9 deletions
diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c index afaebc7..7011c71 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 1eb1a44..b68fa19 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; /* |
