#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
+#include <net/dst.h>
+#include <net/flow.h>
#include <net/ipv6.h>
+#include <net/route.h>
#include <net/tcp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
-MODULE_DESCRIPTION("x_tables TCP MSS modification module");
+MODULE_DESCRIPTION("Xtables: TCP Maximum Segment Size (MSS) adjustment");
MODULE_ALIAS("ipt_TCPMSS");
MODULE_ALIAS("ip6t_TCPMSS");
static int
tcpmss_mangle_packet(struct sk_buff *skb,
const struct xt_tcpmss_info *info,
+ unsigned int in_mtu,
unsigned int tcphoff,
unsigned int minlen)
{
tcplen = skb->len - tcphoff;
tcph = (struct tcphdr *)(skb_network_header(skb) + 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",
- skb->len);
+ /* Header cannot be larger than the packet */
+ if (tcplen < tcph->doff*4)
return -1;
- }
if (info->mss == XT_TCPMSS_CLAMP_PMTU) {
- if (dst_mtu(skb->dst) <= minlen) {
+ if (dst_mtu(skb_dst(skb)) <= minlen) {
if (net_ratelimit())
printk(KERN_ERR "xt_TCPMSS: "
"unknown or invalid path-MTU (%u)\n",
- dst_mtu(skb->dst));
+ dst_mtu(skb_dst(skb)));
+ return -1;
+ }
+ if (in_mtu <= minlen) {
+ if (net_ratelimit())
+ printk(KERN_ERR "xt_TCPMSS: unknown or "
+ "invalid path-MTU (%u)\n", in_mtu);
return -1;
}
- newmss = dst_mtu(skb->dst) - minlen;
+ newmss = min(dst_mtu(skb_dst(skb)), in_mtu) - minlen;
} else
newmss = info->mss;
oldmss = (opt[i+2] << 8) | opt[i+3];
- if (info->mss == XT_TCPMSS_CLAMP_PMTU &&
- oldmss <= newmss)
+ /* Never increase MSS, even when setting it, as
+ * doing so results in problems for hosts that rely
+ * on MSS being set correctly.
+ */
+ if (oldmss <= newmss)
return 0;
opt[i+2] = (newmss & 0xff00) >> 8;
opt[i+3] = newmss & 0x00ff;
- nf_proto_csum_replace2(&tcph->check, skb,
- htons(oldmss), htons(newmss), 0);
+ inet_proto_csum_replace2(&tcph->check, skb,
+ htons(oldmss), htons(newmss),
+ 0);
return 0;
}
}
+ /* 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)
+ return 0;
+
/*
* MSS Option not found ?! add it..
*/
opt = (u_int8_t *)tcph + sizeof(struct tcphdr);
memmove(opt + TCPOLEN_MSS, opt, tcplen - sizeof(struct tcphdr));
- nf_proto_csum_replace2(&tcph->check, skb,
- htons(tcplen), htons(tcplen + TCPOLEN_MSS), 1);
+ inet_proto_csum_replace2(&tcph->check, skb,
+ 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, skb, 0, *((__be32 *)opt), 0);
+ inet_proto_csum_replace4(&tcph->check, skb, 0, *((__be32 *)opt), 0);
oldval = ((__be16 *)tcph)[6];
tcph->doff += TCPOLEN_MSS/4;
- nf_proto_csum_replace2(&tcph->check, skb,
- oldval, ((__be16 *)tcph)[6], 0);
+ inet_proto_csum_replace2(&tcph->check, skb,
+ oldval, ((__be16 *)tcph)[6], 0);
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)
+ fl.fl4_dst = ip_hdr(skb)->saddr;
+ else
+ fl.fl6_dst = ipv6_hdr(skb)->saddr;
+
+ rcu_read_lock();
+ ai = nf_get_afinfo(family);
+ if (ai != NULL)
+ ai->route((struct dst_entry **)&rt, &fl);
+ rcu_read_unlock();
+
+ if (rt != NULL) {
+ mtu = dst_mtu(&rt->u.dst);
+ dst_release(&rt->u.dst);
+ }
+ return mtu;
+}
+
static unsigned int
-xt_tcpmss_target4(struct sk_buff *skb,
- const struct net_device *in,
- const struct net_device *out,
- unsigned int hooknum,
- const struct xt_target *target,
- const void *targinfo)
+tcpmss_tg4(struct sk_buff *skb, const struct xt_target_param *par)
{
struct iphdr *iph = ip_hdr(skb);
__be16 newlen;
int ret;
- ret = tcpmss_mangle_packet(skb, targinfo, iph->ihl * 4,
+ ret = tcpmss_mangle_packet(skb, par->targinfo,
+ tcpmss_reverse_mtu(skb, PF_INET),
+ iph->ihl * 4,
sizeof(*iph) + sizeof(struct tcphdr));
if (ret < 0)
return NF_DROP;
if (ret > 0) {
iph = ip_hdr(skb);
newlen = htons(ntohs(iph->tot_len) + ret);
- nf_csum_replace2(&iph->check, iph->tot_len, newlen);
+ 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 *skb,
- const struct net_device *in,
- const struct net_device *out,
- unsigned int hooknum,
- const struct xt_target *target,
- const void *targinfo)
+tcpmss_tg6(struct sk_buff *skb, const struct xt_target_param *par)
{
struct ipv6hdr *ipv6h = ipv6_hdr(skb);
u8 nexthdr;
tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr);
if (tcphoff < 0)
return NF_DROP;
- ret = tcpmss_mangle_packet(skb, targinfo, tcphoff,
+ ret = tcpmss_mangle_packet(skb, par->targinfo,
+ tcpmss_reverse_mtu(skb, PF_INET6),
+ tcphoff,
sizeof(*ipv6h) + sizeof(struct tcphdr));
if (ret < 0)
return NF_DROP;
return false;
}
-static bool
-xt_tcpmss_checkentry4(const char *tablename,
- const void *entry,
- const struct xt_target *target,
- void *targinfo,
- unsigned int hook_mask)
+static bool tcpmss_tg4_check(const struct xt_tgchk_param *par)
{
- const struct xt_tcpmss_info *info = targinfo;
- const struct ipt_entry *e = entry;
+ const struct xt_tcpmss_info *info = par->targinfo;
+ const struct ipt_entry *e = par->entryinfo;
+ const struct xt_entry_match *ematch;
if (info->mss == XT_TCPMSS_CLAMP_PMTU &&
- (hook_mask & ~((1 << NF_IP_FORWARD) |
- (1 << NF_IP_LOCAL_OUT) |
- (1 << NF_IP_POST_ROUTING))) != 0) {
+ (par->hook_mask & ~((1 << NF_INET_FORWARD) |
+ (1 << NF_INET_LOCAL_OUT) |
+ (1 << NF_INET_POST_ROUTING))) != 0) {
printk("xt_TCPMSS: path-MTU clamping only supported in "
"FORWARD, OUTPUT and POSTROUTING hooks\n");
return false;
}
- if (IPT_MATCH_ITERATE(e, find_syn_match))
- return true;
+ xt_ematch_foreach(ematch, e)
+ if (find_syn_match(ematch))
+ return true;
printk("xt_TCPMSS: Only works on TCP SYN packets\n");
return false;
}
#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
-static bool
-xt_tcpmss_checkentry6(const char *tablename,
- const void *entry,
- const struct xt_target *target,
- void *targinfo,
- unsigned int hook_mask)
+static bool tcpmss_tg6_check(const struct xt_tgchk_param *par)
{
- const struct xt_tcpmss_info *info = targinfo;
- const struct ip6t_entry *e = entry;
+ const struct xt_tcpmss_info *info = par->targinfo;
+ const struct ip6t_entry *e = par->entryinfo;
+ const struct xt_entry_match *ematch;
if (info->mss == XT_TCPMSS_CLAMP_PMTU &&
- (hook_mask & ~((1 << NF_IP6_FORWARD) |
- (1 << NF_IP6_LOCAL_OUT) |
- (1 << NF_IP6_POST_ROUTING))) != 0) {
+ (par->hook_mask & ~((1 << NF_INET_FORWARD) |
+ (1 << NF_INET_LOCAL_OUT) |
+ (1 << NF_INET_POST_ROUTING))) != 0) {
printk("xt_TCPMSS: path-MTU clamping only supported in "
"FORWARD, OUTPUT and POSTROUTING hooks\n");
return false;
}
- if (IP6T_MATCH_ITERATE(e, find_syn_match))
- return true;
+ xt_ematch_foreach(ematch, e)
+ if (find_syn_match(ematch))
+ return true;
printk("xt_TCPMSS: Only works on TCP SYN packets\n");
return false;
}
#endif
-static struct xt_target xt_tcpmss_reg[] __read_mostly = {
+static struct xt_target tcpmss_tg_reg[] __read_mostly = {
{
- .family = AF_INET,
+ .family = NFPROTO_IPV4,
.name = "TCPMSS",
- .checkentry = xt_tcpmss_checkentry4,
- .target = xt_tcpmss_target4,
+ .checkentry = tcpmss_tg4_check,
+ .target = tcpmss_tg4,
.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,
+ .family = NFPROTO_IPV6,
.name = "TCPMSS",
- .checkentry = xt_tcpmss_checkentry6,
- .target = xt_tcpmss_target6,
+ .checkentry = tcpmss_tg6_check,
+ .target = tcpmss_tg6,
.targetsize = sizeof(struct xt_tcpmss_info),
.proto = IPPROTO_TCP,
.me = THIS_MODULE,
#endif
};
-static int __init xt_tcpmss_init(void)
+static int __init tcpmss_tg_init(void)
{
- return xt_register_targets(xt_tcpmss_reg, ARRAY_SIZE(xt_tcpmss_reg));
+ return xt_register_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg));
}
-static void __exit xt_tcpmss_fini(void)
+static void __exit tcpmss_tg_exit(void)
{
- xt_unregister_targets(xt_tcpmss_reg, ARRAY_SIZE(xt_tcpmss_reg));
+ xt_unregister_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg));
}
-module_init(xt_tcpmss_init);
-module_exit(xt_tcpmss_fini);
+module_init(tcpmss_tg_init);
+module_exit(tcpmss_tg_exit);
Code Review / linux-2.6.git / blobdiff