diff options
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/netfilter/Kconfig | 26 | ||||
| -rw-r--r-- | net/ipv4/netfilter/Makefile | 1 | ||||
| -rw-r--r-- | net/ipv4/netfilter/ipt_TCPMSS.c | 207 | ||||
| -rw-r--r-- | net/netfilter/Kconfig | 26 | ||||
| -rw-r--r-- | net/netfilter/Makefile | 1 | ||||
| -rw-r--r-- | net/netfilter/xt_TCPMSS.c | 296 |
6 files changed, 323 insertions, 234 deletions
diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig index 47bd3ad18b71..9b08e7ad71bc 100644 --- a/net/ipv4/netfilter/Kconfig +++ b/net/ipv4/netfilter/Kconfig @@ -361,32 +361,6 @@ config IP_NF_TARGET_ULOG To compile it as a module, choose M here. If unsure, say N. -config IP_NF_TARGET_TCPMSS - tristate "TCPMSS target support" - depends on IP_NF_IPTABLES - ---help--- - This option adds a `TCPMSS' target, which allows you to alter the - MSS value of TCP SYN packets, to control the maximum size for that - connection (usually limiting it to your outgoing interface's MTU - minus 40). - - This is used to overcome criminally braindead ISPs or servers which - block ICMP Fragmentation Needed packets. The symptoms of this - problem are that everything works fine from your Linux - firewall/router, but machines behind it can never exchange large - packets: - 1) Web browsers connect, then hang with no data received. - 2) Small mail works fine, but large emails hang. - 3) ssh works fine, but scp hangs after initial handshaking. - - Workaround: activate this option and add a rule to your firewall - configuration like: - - iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN \ - -j TCPMSS --clamp-mss-to-pmtu - - To compile it as a module, choose M here. If unsure, say N. - # NAT + specific targets: ip_conntrack config IP_NF_NAT tristate "Full NAT" diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile index 16d177b71bf8..6625ec68180c 100644 --- a/net/ipv4/netfilter/Makefile +++ b/net/ipv4/netfilter/Makefile @@ -103,7 +103,6 @@ obj-$(CONFIG_IP_NF_TARGET_SAME) += ipt_SAME.o obj-$(CONFIG_IP_NF_NAT_SNMP_BASIC) += ip_nat_snmp_basic.o obj-$(CONFIG_IP_NF_TARGET_LOG) += ipt_LOG.o obj-$(CONFIG_IP_NF_TARGET_ULOG) += ipt_ULOG.o -obj-$(CONFIG_IP_NF_TARGET_TCPMSS) += ipt_TCPMSS.o obj-$(CONFIG_IP_NF_TARGET_CLUSTERIP) += ipt_CLUSTERIP.o obj-$(CONFIG_IP_NF_TARGET_TTL) += ipt_TTL.o diff --git a/net/ipv4/netfilter/ipt_TCPMSS.c b/net/ipv4/netfilter/ipt_TCPMSS.c deleted file mode 100644 index 93eb5c3c1884..000000000000 --- a/net/ipv4/netfilter/ipt_TCPMSS.c +++ /dev/null @@ -1,207 +0,0 @@ -/* - * This is a module which is used for setting the MSS option in TCP packets. - * - * Copyright (C) 2000 Marc Boucher <marc@mbsi.ca> - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - */ - -#include <linux/module.h> -#include <linux/skbuff.h> - -#include <linux/ip.h> -#include <net/tcp.h> - -#include <linux/netfilter_ipv4/ip_tables.h> -#include <linux/netfilter_ipv4/ipt_TCPMSS.h> - -MODULE_LICENSE("GPL"); -MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>"); -MODULE_DESCRIPTION("iptables TCP MSS modification module"); - -static inline unsigned int -optlen(const u_int8_t *opt, unsigned int offset) -{ - /* Beware zero-length options: make finite progress */ - if (opt[offset] <= TCPOPT_NOP || opt[offset+1] == 0) - return 1; - else - return opt[offset+1]; -} - -static unsigned int -ipt_tcpmss_target(struct sk_buff **pskb, - const struct net_device *in, - const struct net_device *out, - unsigned int hooknum, - const struct xt_target *target, - const void *targinfo) -{ - const struct ipt_tcpmss_info *tcpmssinfo = targinfo; - struct tcphdr *tcph; - struct iphdr *iph; - u_int16_t tcplen, newmss; - __be16 newtotlen, oldval; - unsigned int i; - u_int8_t *opt; - - if (!skb_make_writable(pskb, (*pskb)->len)) - return NF_DROP; - - iph = (*pskb)->nh.iph; - tcplen = (*pskb)->len - iph->ihl*4; - tcph = (void *)iph + iph->ihl*4; - - /* Since it passed flags test in tcp match, we know it is is - not a fragment, and has data >= tcp header length. SYN - packets should not contain data: if they did, then we risk - running over MTU, sending Frag Needed and breaking things - badly. --RR */ - if (tcplen != tcph->doff*4) { - if (net_ratelimit()) - printk(KERN_ERR - "ipt_tcpmss_target: bad length (%d bytes)\n", - (*pskb)->len); - return NF_DROP; - } - - if (tcpmssinfo->mss == IPT_TCPMSS_CLAMP_PMTU) { - if (dst_mtu((*pskb)->dst) <= sizeof(struct iphdr) + - sizeof(struct tcphdr)) { - if (net_ratelimit()) - printk(KERN_ERR "ipt_tcpmss_target: " - "unknown or invalid path-MTU (%d)\n", - dst_mtu((*pskb)->dst)); - return NF_DROP; /* or IPT_CONTINUE ?? */ - } - - newmss = dst_mtu((*pskb)->dst) - sizeof(struct iphdr) - - sizeof(struct tcphdr); - } else - newmss = tcpmssinfo->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) { - u_int16_t oldmss; - - oldmss = (opt[i+2] << 8) | opt[i+3]; - - if (tcpmssinfo->mss == IPT_TCPMSS_CLAMP_PMTU && - oldmss <= newmss) - return IPT_CONTINUE; - - opt[i+2] = (newmss & 0xff00) >> 8; - opt[i+3] = (newmss & 0x00ff); - - nf_proto_csum_replace2(&tcph->check, *pskb, - htons(oldmss), htons(newmss), 0); - return IPT_CONTINUE; - } - } - - /* - * MSS Option not found ?! add it.. - */ - if (skb_tailroom((*pskb)) < TCPOLEN_MSS) { - struct sk_buff *newskb; - - newskb = skb_copy_expand(*pskb, skb_headroom(*pskb), - TCPOLEN_MSS, GFP_ATOMIC); - if (!newskb) - return NF_DROP; - kfree_skb(*pskb); - *pskb = newskb; - iph = (*pskb)->nh.iph; - tcph = (void *)iph + iph->ihl*4; - } - - skb_put((*pskb), TCPOLEN_MSS); - - opt = (u_int8_t *)tcph + sizeof(struct tcphdr); - memmove(opt + TCPOLEN_MSS, opt, tcplen - sizeof(struct tcphdr)); - - nf_proto_csum_replace2(&tcph->check, *pskb, - htons(tcplen), htons(tcplen + TCPOLEN_MSS), 1); - opt[0] = TCPOPT_MSS; - opt[1] = TCPOLEN_MSS; - opt[2] = (newmss & 0xff00) >> 8; - opt[3] = (newmss & 0x00ff); - - nf_proto_csum_replace4(&tcph->check, *pskb, 0, *((__be32 *)opt), 0); - - oldval = ((__be16 *)tcph)[6]; - tcph->doff += TCPOLEN_MSS/4; - nf_proto_csum_replace2(&tcph->check, *pskb, - oldval, ((__be16 *)tcph)[6], 0); - - newtotlen = htons(ntohs(iph->tot_len) + TCPOLEN_MSS); - nf_csum_replace2(&iph->check, iph->tot_len, newtotlen); - iph->tot_len = newtotlen; - return IPT_CONTINUE; -} - -#define TH_SYN 0x02 - -static inline int find_syn_match(const struct ipt_entry_match *m) -{ - const struct ipt_tcp *tcpinfo = (const struct ipt_tcp *)m->data; - - if (strcmp(m->u.kernel.match->name, "tcp") == 0 && - tcpinfo->flg_cmp & TH_SYN && - !(tcpinfo->invflags & IPT_TCP_INV_FLAGS)) - return 1; - - return 0; -} - -/* Must specify -p tcp --syn/--tcp-flags SYN */ -static int -ipt_tcpmss_checkentry(const char *tablename, - const void *e_void, - const struct xt_target *target, - void *targinfo, - unsigned int hook_mask) -{ - const struct ipt_tcpmss_info *tcpmssinfo = targinfo; - const struct ipt_entry *e = e_void; - - if (tcpmssinfo->mss == IPT_TCPMSS_CLAMP_PMTU && - (hook_mask & ~((1 << NF_IP_FORWARD) | - (1 << NF_IP_LOCAL_OUT) | - (1 << NF_IP_POST_ROUTING))) != 0) { - printk("TCPMSS: path-MTU clamping only supported in " - "FORWARD, OUTPUT and POSTROUTING hooks\n"); - return 0; - } - - if (IPT_MATCH_ITERATE(e, find_syn_match)) - return 1; - printk("TCPMSS: Only works on TCP SYN packets\n"); - return 0; -} - -static struct ipt_target ipt_tcpmss_reg = { - .name = "TCPMSS", - .target = ipt_tcpmss_target, - .targetsize = sizeof(struct ipt_tcpmss_info), - .proto = IPPROTO_TCP, - .checkentry = ipt_tcpmss_checkentry, - .me = THIS_MODULE, -}; - -static int __init ipt_tcpmss_init(void) -{ - return ipt_register_target(&ipt_tcpmss_reg); -} - -static void __exit ipt_tcpmss_fini(void) -{ - ipt_unregister_target(&ipt_tcpmss_reg); -} - -module_init(ipt_tcpmss_init); -module_exit(ipt_tcpmss_fini); diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig index 614c92c17835..748f7f00909a 100644 --- a/net/netfilter/Kconfig +++ b/net/netfilter/Kconfig @@ -395,6 +395,32 @@ config NETFILTER_XT_TARGET_CONNSECMARK To compile it as a module, choose M here. If unsure, say N. +config NETFILTER_XT_TARGET_TCPMSS + tristate '"TCPMSS" target support' + depends on NETFILTER_XTABLES && (IPV6 || IPV6=n) + ---help--- + This option adds a `TCPMSS' target, which allows you to alter the + MSS value of TCP SYN packets, to control the maximum size for that + connection (usually limiting it to your outgoing interface's MTU + minus 40). + + This is used to overcome criminally braindead ISPs or servers which + block ICMP Fragmentation Needed packets. The symptoms of this + problem are that everything works fine from your Linux + firewall/router, but machines behind it can never exchange large + packets: + 1) Web browsers connect, then hang with no data received. + 2) Small mail works fine, but large emails hang. + 3) ssh works fine, but scp hangs after initial handshaking. + + Workaround: activate this option and add a rule to your firewall + configuration like: + + iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN \ + -j TCPMSS --clamp-mss-to-pmtu + + To compile it as a module, choose M here. If unsure, say N. + config NETFILTER_XT_MATCH_COMMENT tristate '"comment" match support' depends on NETFILTER_XTABLES diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile index 5054b0ff8096..b2b5c7566b26 100644 --- a/net/netfilter/Makefile +++ b/net/netfilter/Makefile @@ -45,6 +45,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_NFQUEUE) += xt_NFQUEUE.o obj-$(CONFIG_NETFILTER_XT_TARGET_NFLOG) += xt_NFLOG.o obj-$(CONFIG_NETFILTER_XT_TARGET_NOTRACK) += xt_NOTRACK.o obj-$(CONFIG_NETFILTER_XT_TARGET_SECMARK) += xt_SECMARK.o +obj-$(CONFIG_NETFILTER_XT_TARGET_TCPMSS) += xt_TCPMSS.o obj-$(CONFIG_NETFILTER_XT_TARGET_CONNSECMARK) += xt_CONNSECMARK.o # matches diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c new file mode 100644 index 000000000000..db7e38c08de2 --- /dev/null +++ b/net/netfilter/xt_TCPMSS.c @@ -0,0 +1,296 @@ +/* + * This is a module which is used for setting the MSS option in TCP packets. + * + * Copyright (C) 2000 Marc Boucher <marc@mbsi.ca> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/module.h> +#include <linux/skbuff.h> +#include <linux/ip.h> +#include <linux/ipv6.h> +#include <linux/tcp.h> +#include <net/ipv6.h> +#include <net/tcp.h> + +#include <linux/netfilter_ipv4/ip_tables.h> +#include <linux/netfilter_ipv6/ip6_tables.h> +#include <linux/netfilter/x_tables.h> +#include <linux/netfilter/xt_tcpudp.h> +#include <linux/netfilter/xt_TCPMSS.h> + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>"); +MODULE_DESCRIPTION("x_tables TCP MSS modification module"); +MODULE_ALIAS("ipt_TCPMSS"); +MODULE_ALIAS("ip6t_TCPMSS"); + +static inline unsigned int +optlen(const u_int8_t *opt, unsigned int offset) +{ + /* Beware zero-length options: make finite progress */ + if (opt[offset] <= TCPOPT_NOP || opt[offset+1] == 0) + return 1; + else + return opt[offset+1]; +} + +static int +tcpmss_mangle_packet(struct sk_buff **pskb, + const struct xt_tcpmss_info *info, + unsigned int tcphoff, + unsigned int minlen) +{ + struct tcphdr *tcph; + unsigned int tcplen, i; + __be16 oldval; + u16 newmss; + u8 *opt; + + if (!skb_make_writable(pskb, (*pskb)->len)) + return -1; + + tcplen = (*pskb)->len - tcphoff; + tcph = (struct tcphdr *)((*pskb)->nh.raw + tcphoff); + + /* Since it passed flags test in tcp match, we know it is is + not a fragment, and has data >= tcp header length. SYN + packets should not contain data: if they did, then we risk + running over MTU, sending Frag Needed and breaking things + badly. --RR */ + if (tcplen != tcph->doff*4) { + if (net_ratelimit()) + printk(KERN_ERR "xt_TCPMSS: bad length (%u bytes)\n", + (*pskb)->len); + return -1; + } + + if (info->mss == XT_TCPMSS_CLAMP_PMTU) { + if (dst_mtu((*pskb)->dst) <= minlen) { + if (net_ratelimit()) + printk(KERN_ERR "xt_TCPMSS: " + "unknown or invalid path-MTU (%u)\n", + dst_mtu((*pskb)->dst)); + return -1; + } + newmss = dst_mtu((*pskb)->dst) - minlen; + } else + 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) { + u_int16_t oldmss; + + oldmss = (opt[i+2] << 8) | opt[i+3]; + + if (info->mss == XT_TCPMSS_CLAMP_PMTU && + oldmss <= newmss) + return 0; + + opt[i+2] = (newmss & 0xff00) >> 8; + opt[i+3] = (newmss & 0x00ff); + + nf_proto_csum_replace2(&tcph->check, *pskb, + htons(oldmss), htons(newmss), 0); + return 0; + } + } + + /* + * MSS Option not found ?! add it.. + */ + if (skb_tailroom((*pskb)) < TCPOLEN_MSS) { + struct sk_buff *newskb; + + newskb = skb_copy_expand(*pskb, skb_headroom(*pskb), + TCPOLEN_MSS, GFP_ATOMIC); + if (!newskb) + return -1; + kfree_skb(*pskb); + *pskb = newskb; + tcph = (struct tcphdr *)((*pskb)->nh.raw + tcphoff); + } + + skb_put((*pskb), TCPOLEN_MSS); + + opt = (u_int8_t *)tcph + sizeof(struct tcphdr); + memmove(opt + TCPOLEN_MSS, opt, tcplen - sizeof(struct tcphdr)); + + nf_proto_csum_replace2(&tcph->check, *pskb, + htons(tcplen), htons(tcplen + TCPOLEN_MSS), 1); + opt[0] = TCPOPT_MSS; + opt[1] = TCPOLEN_MSS; + opt[2] = (newmss & 0xff00) >> 8; + opt[3] = (newmss & 0x00ff); + + nf_proto_csum_replace4(&tcph->check, *pskb, 0, *((__be32 *)opt), 0); + + oldval = ((__be16 *)tcph)[6]; + tcph->doff += TCPOLEN_MSS/4; + nf_proto_csum_replace2(&tcph->check, *pskb, + oldval, ((__be16 *)tcph)[6], 0); + return TCPOLEN_MSS; +} + +static unsigned int +xt_tcpmss_target4(struct sk_buff **pskb, + const struct net_device *in, + const struct net_device *out, + unsigned int hooknum, + const struct xt_target *target, + const void *targinfo) +{ + struct iphdr *iph = (*pskb)->nh.iph; + __be16 newlen; + int ret; + + ret = tcpmss_mangle_packet(pskb, targinfo, iph->ihl * 4, + sizeof(*iph) + sizeof(struct tcphdr)); + if (ret < 0) + return NF_DROP; + if (ret > 0) { + iph = (*pskb)->nh.iph; + newlen = htons(ntohs(iph->tot_len) + ret); + nf_csum_replace2(&iph->check, iph->tot_len, newlen); + iph->tot_len = newlen; + } + return XT_CONTINUE; +} + +#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE) +static unsigned int +xt_tcpmss_target6(struct sk_buff **pskb, + const struct net_device *in, + const struct net_device *out, + unsigned int hooknum, + const struct xt_target *target, + const void *targinfo) +{ + struct ipv6hdr *ipv6h = (*pskb)->nh.ipv6h; + u8 nexthdr; + int tcphoff; + int ret; + + nexthdr = ipv6h->nexthdr; + tcphoff = ipv6_skip_exthdr(*pskb, sizeof(*ipv6h), &nexthdr); + if (tcphoff < 0) { + WARN_ON(1); + return NF_DROP; + } + ret = tcpmss_mangle_packet(pskb, targinfo, tcphoff, + sizeof(*ipv6h) + sizeof(struct tcphdr)); + if (ret < 0) + return NF_DROP; + if (ret > 0) { + ipv6h = (*pskb)->nh.ipv6h; + ipv6h->payload_len = htons(ntohs(ipv6h->payload_len) + ret); + } + return XT_CONTINUE; +} +#endif + +#define TH_SYN 0x02 + +/* Must specify -p tcp --syn */ +static inline int find_syn_match(const struct xt_entry_match *m) +{ + const struct xt_tcp *tcpinfo = (const struct xt_tcp *)m->data; + + if (strcmp(m->u.kernel.match->name, "tcp") == 0 && + tcpinfo->flg_cmp & TH_SYN && + !(tcpinfo->invflags & XT_TCP_INV_FLAGS)) + return 1; + + return 0; +} + +static int +xt_tcpmss_checkentry4(const char *tablename, + const void *entry, + const struct xt_target *target, + void *targinfo, + unsigned int hook_mask) +{ + const struct xt_tcpmss_info *info = targinfo; + const struct ipt_entry *e = entry; + + if (info->mss == XT_TCPMSS_CLAMP_PMTU && + (hook_mask & ~((1 << NF_IP_FORWARD) | + (1 << NF_IP_LOCAL_OUT) | + (1 << NF_IP_POST_ROUTING))) != 0) { + printk("xt_TCPMSS: path-MTU clamping only supported in " + "FORWARD, OUTPUT and POSTROUTING hooks\n"); + return 0; + } + if (IPT_MATCH_ITERATE(e, find_syn_match)) + return 1; + printk("xt_TCPMSS: Only works on TCP SYN packets\n"); + return 0; +} + +#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE) +static int +xt_tcpmss_checkentry6(const char *tablename, + const void *entry, + const struct xt_target *target, + void *targinfo, + unsigned int hook_mask) +{ + const struct xt_tcpmss_info *info = targinfo; + const struct ip6t_entry *e = entry; + + if (info->mss == XT_TCPMSS_CLAMP_PMTU && + (hook_mask & ~((1 << NF_IP6_FORWARD) | + (1 << NF_IP6_LOCAL_OUT) | + (1 << NF_IP6_POST_ROUTING))) != 0) { + printk("xt_TCPMSS: path-MTU clamping only supported in " + "FORWARD, OUTPUT and POSTROUTING hooks\n"); + return 0; + } + if (IP6T_MATCH_ITERATE(e, find_syn_match)) + return 1; + printk("xt_TCPMSS: Only works on TCP SYN packets\n"); + return 0; +} +#endif + +static struct xt_target xt_tcpmss_reg[] = { + { + .family = AF_INET, + .name = "TCPMSS", + .checkentry = xt_tcpmss_checkentry4, + .target = xt_tcpmss_target4, + .targetsize = sizeof(struct xt_tcpmss_info), + .proto = IPPROTO_TCP, + .me = THIS_MODULE, + }, +#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE) + { + .family = AF_INET6, + .name = "TCPMSS", + .checkentry = xt_tcpmss_checkentry6, + .target = xt_tcpmss_target6, + .targetsize = sizeof(struct xt_tcpmss_info), + .proto = IPPROTO_TCP, + .me = THIS_MODULE, + }, +#endif +}; + +static int __init xt_tcpmss_init(void) +{ + return xt_register_targets(xt_tcpmss_reg, ARRAY_SIZE(xt_tcpmss_reg)); +} + +static void __exit xt_tcpmss_fini(void) +{ + xt_unregister_targets(xt_tcpmss_reg, ARRAY_SIZE(xt_tcpmss_reg)); +} + +module_init(xt_tcpmss_init); +module_exit(xt_tcpmss_fini); |