syncookies: remove last_synq_overflow from struct tcp_sock

last_synq_overflow eats 4 or 8 bytes in struct tcp_sock, even
though it is only used when a listening sockets syn queue
is full.

We can (ab)use rx_opt.ts_recent_stamp to store the same information;
it is not used otherwise as long as a socket is in listen state.

Move linger2 around to avoid splitting struct mtu_probe
across cacheline boundary on 32 bit arches.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 18 insertions, 8 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 9d5078bd23a3..8afac76cd748 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -377,7 +377,7 @@ struct tcp_sock {
         unsigned int            keepalive_time;   /* time before keep alive takes place */
         unsigned int            keepalive_intvl;  /* time interval between keep alive probes */
 
-        unsigned long last_synq_overflow; 
+        int                     linger2;
 
 /* Receiver side RTT estimation */
         struct {
@@ -406,8 +406,6 @@ struct tcp_sock {
 /* TCP MD5 Signagure Option information */
         struct tcp_md5sig_info  *md5sig_info;
 #endif
-
-        int                     linger2;
 };
 
 static inline struct tcp_sock *tcp_sk(const struct sock *sk)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1b94b9bfe2dc..b55b4891029e 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -265,6 +265,19 @@ static inline int tcp_too_many_orphans(struct sock *sk, int num)
                  atomic_read(&tcp_memory_allocated) > sysctl_tcp_mem[2]);
 }
 
+/* syncookies: remember time of last synqueue overflow */
+static inline void tcp_synq_overflow(struct sock *sk)
+{
+        tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
+}
+
+/* syncookies: no recent synqueue overflow on this listening socket? */
+static inline int tcp_synq_no_recent_overflow(const struct sock *sk)
+{
+        unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
+        return time_after(jiffies, last_overflow + TCP_TIMEOUT_INIT);
+}
+
 extern struct proto tcp_prot;
 
 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index b35a950d2e06..cd2b97f1b6e1 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -161,13 +161,12 @@ static __u16 const msstab[] = {
  */
 __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp)
 {
-        struct tcp_sock *tp = tcp_sk(sk);
         const struct iphdr *iph = ip_hdr(skb);
         const struct tcphdr *th = tcp_hdr(skb);
         int mssind;
         const __u16 mss = *mssp;
 
-        tp->last_synq_overflow = jiffies;
+        tcp_synq_overflow(sk);
 
         /* XXX sort msstab[] by probability?  Binary search? */
         for (mssind = 0; mss > msstab[mssind + 1]; mssind++)
@@ -268,7 +267,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
         if (!sysctl_tcp_syncookies || !th->ack)
                 goto out;
 
-        if (time_after(jiffies, tp->last_synq_overflow + TCP_TIMEOUT_INIT) ||
+        if (tcp_synq_no_recent_overflow(sk) ||
             (mss = cookie_check(skb, cookie)) == 0) {
                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
                 goto out;
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 711175e0571f..8c2513982b61 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -131,7 +131,7 @@ __u32 cookie_v6_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp)
         int mssind;
         const __u16 mss = *mssp;
 
-        tcp_sk(sk)->last_synq_overflow = jiffies;
+        tcp_synq_overflow(sk);
 
         for (mssind = 0; mss > msstab[mssind + 1]; mssind++)
                 ;
@@ -175,7 +175,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
         if (!sysctl_tcp_syncookies || !th->ack)
                 goto out;
 
-        if (time_after(jiffies, tp->last_synq_overflow + TCP_TIMEOUT_INIT) ||
+        if (tcp_synq_no_recent_overflow(sk) ||
                 (mss = cookie_check(skb, cookie)) == 0) {
                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
                 goto out;