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>

1 files changed, 13 insertions, 0 deletions

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)