net: syncookies: export cookie_v4_init_sequence/cookie_v4_check

Extract the local TCP stack independant parts of tcp_v4_init_sequence()
and cookie_v4_check() and export them for use by the upcoming SYNPROXY
target.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: David S. Miller <davem@davemloft.net>
Tested-by: Martin Topholm <mph@one.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

2 files changed, 22 insertions, 11 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 09cb5c11ceea..8e2b63678a83 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -476,9 +476,13 @@ void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
 
 /* From syncookies.c */
 extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
+extern int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
+                             u32 cookie);
 extern struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, 
                                     struct ip_options *opt);
 #ifdef CONFIG_SYN_COOKIES
+extern u32 __cookie_v4_init_sequence(const struct iphdr *iph,
+                                     const struct tcphdr *th, u16 *mssp);
 extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, 
                                      __u16 *mss);
 #else
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index b05c96e7af8b..14a15c49129d 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -160,26 +160,33 @@ static __u16 const msstab[] = {
  * Generate a syncookie.  mssp points to the mss, which is returned
  * rounded down to the value encoded in the cookie.
  */
-__u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp)
+u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
+                              u16 *mssp)
 {
-        const struct iphdr *iph = ip_hdr(skb);
-        const struct tcphdr *th = tcp_hdr(skb);
         int mssind;
         const __u16 mss = *mssp;
 
-        tcp_synq_overflow(sk);
-
         for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
                 if (mss >= msstab[mssind])
                         break;
         *mssp = msstab[mssind];
 
-        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
-
         return secure_tcp_syn_cookie(iph->saddr, iph->daddr,
                                      th->source, th->dest, ntohl(th->seq),
                                      jiffies / (HZ * 60), mssind);
 }
+EXPORT_SYMBOL_GPL(__cookie_v4_init_sequence);
+
+__u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp)
+{
+        const struct iphdr *iph = ip_hdr(skb);
+        const struct tcphdr *th = tcp_hdr(skb);
+
+        tcp_synq_overflow(sk);
+        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
+
+        return __cookie_v4_init_sequence(iph, th, mssp);
+}
 
 /*
  * This (misnamed) value is the age of syncookie which is permitted.
@@ -192,10 +199,9 @@ __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp)
  * Check if a ack sequence number is a valid syncookie.
  * Return the decoded mss if it is, or 0 if not.
  */
-static inline int cookie_check(struct sk_buff *skb, __u32 cookie)
+int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
+                      u32 cookie)
 {
-        const struct iphdr *iph = ip_hdr(skb);
-        const struct tcphdr *th = tcp_hdr(skb);
         __u32 seq = ntohl(th->seq) - 1;
         __u32 mssind = check_tcp_syn_cookie(cookie, iph->saddr, iph->daddr,
                                             th->source, th->dest, seq,
@@ -204,6 +210,7 @@ static inline int cookie_check(struct sk_buff *skb, __u32 cookie)
 
         return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
 }
+EXPORT_SYMBOL_GPL(__cookie_v4_check);
 
 static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
                                            struct request_sock *req,
@@ -284,7 +291,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
                 goto out;
 
         if (tcp_synq_no_recent_overflow(sk) ||
-            (mss = cookie_check(skb, cookie)) == 0) {
+            (mss = __cookie_v4_check(ip_hdr(skb), th, cookie)) == 0) {
                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
                 goto out;
         }