diff options
Diffstat (limited to 'net/netfilter/xt_TCPMSS.c')
| -rw-r--r-- | net/netfilter/xt_TCPMSS.c | 102 |
1 files changed, 55 insertions, 47 deletions
diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c index 7011c71646f..e762de5ee89 100644 --- a/net/netfilter/xt_TCPMSS.c +++ b/net/netfilter/xt_TCPMSS.c @@ -43,35 +43,74 @@ optlen(const u_int8_t *opt, unsigned int offset) return opt[offset+1]; } +static u_int32_t tcpmss_reverse_mtu(struct net *net, + 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(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) { const struct xt_tcpmss_info *info = par->targinfo; struct tcphdr *tcph; - unsigned int tcplen, i; + int len, tcp_hdrlen; + unsigned int i; __be16 oldval; u16 newmss; u8 *opt; /* This is a fragment, no TCP header is available */ if (par->fragoff != 0) - return XT_CONTINUE; + return 0; if (!skb_make_writable(skb, skb->len)) return -1; - tcplen = skb->len - tcphoff; + len = skb->len - tcphoff; + if (len < (int)sizeof(struct tcphdr)) + return -1; + tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff); + tcp_hdrlen = tcph->doff * 4; - /* Header cannot be larger than the packet */ - if (tcplen < tcph->doff*4) + if (len < tcp_hdrlen) return -1; if (info->mss == XT_TCPMSS_CLAMP_PMTU) { + struct net *net = dev_net(par->in ? par->in : par->out); + unsigned int in_mtu = tcpmss_reverse_mtu(net, skb, family); + if (dst_mtu(skb_dst(skb)) <= minlen) { net_err_ratelimited("unknown or invalid path-MTU (%u)\n", dst_mtu(skb_dst(skb))); @@ -87,9 +126,8 @@ tcpmss_mangle_packet(struct sk_buff *skb, newmss = info->mss; opt = (u_int8_t *)tcph; - for (i = sizeof(struct tcphdr); i < tcph->doff*4; i += optlen(opt, i)) { - if (opt[i] == TCPOPT_MSS && tcph->doff*4 - i >= TCPOLEN_MSS && - opt[i+1] == TCPOLEN_MSS) { + for (i = sizeof(struct tcphdr); i <= tcp_hdrlen - TCPOLEN_MSS; i += optlen(opt, i)) { + if (opt[i] == TCPOPT_MSS && opt[i+1] == TCPOLEN_MSS) { u_int16_t oldmss; oldmss = (opt[i+2] << 8) | opt[i+3]; @@ -112,9 +150,10 @@ tcpmss_mangle_packet(struct sk_buff *skb, } /* There is data after the header so the option can't be added - without moving it, and doing so may make the SYN packet - itself too large. Accept the packet unmodified instead. */ - if (tcplen > tcph->doff*4) + * without moving it, and doing so may make the SYN packet + * itself too large. Accept the packet unmodified instead. + */ + if (len > tcp_hdrlen) return 0; /* @@ -143,10 +182,10 @@ tcpmss_mangle_packet(struct sk_buff *skb, newmss = min(newmss, (u16)1220); opt = (u_int8_t *)tcph + sizeof(struct tcphdr); - memmove(opt + TCPOLEN_MSS, opt, tcplen - sizeof(struct tcphdr)); + memmove(opt + TCPOLEN_MSS, opt, len - sizeof(struct tcphdr)); inet_proto_csum_replace2(&tcph->check, skb, - htons(tcplen), htons(tcplen + TCPOLEN_MSS), 1); + htons(len), htons(len + TCPOLEN_MSS), 1); opt[0] = TCPOPT_MSS; opt[1] = TCPOLEN_MSS; opt[2] = (newmss & 0xff00) >> 8; @@ -161,37 +200,6 @@ 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) { @@ -200,7 +208,7 @@ 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) @@ -229,7 +237,7 @@ 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) |