Commit a0f82f64 authored by Florian Westphal's avatar Florian Westphal Committed by David S. Miller
Browse files

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: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7eebb0b2

include/linux/tcp.h

+1 −3
Original line number Diff line number Diff line
@@ -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)

include/net/tcp.h

+13 −0
Original line number Diff line number Diff line
@@ -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)

net/ipv4/syncookies.c

+2 −3
Original line number Diff line number Diff line
@@ -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;

net/ipv6/syncookies.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

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