diff options
Diffstat (limited to 'net/ipv4/syncookies.c')
| -rw-r--r-- | net/ipv4/syncookies.c | 38 |
1 files changed, 19 insertions, 19 deletions
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index c9dac8615958..a7cbcc4b726b 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -138,23 +138,23 @@ static __u32 check_tcp_syn_cookie(__u32 cookie, __be32 saddr, __be32 daddr, } /* - * This table has to be sorted and terminated with (__u16)-1. - * XXX generate a better table. - * Unresolved Issues: HIPPI with a 64k MSS is not well supported. + * MSS Values are taken from the 2009 paper + * 'Measuring TCP Maximum Segment Size' by S. Alcock and R. Nelson: + * - values 1440 to 1460 accounted for 80% of observed mss values + * - values outside the 536-1460 range are rare (<0.2%). + * + * Table must be sorted. */ static __u16 const msstab[] = { - 64 - 1, - 256 - 1, - 512 - 1, - 536 - 1, - 1024 - 1, - 1440 - 1, - 1460 - 1, - 4312 - 1, - (__u16)-1 + 64, + 512, + 536, + 1024, + 1440, + 1460, + 4312, + 8960, }; -/* The number doesn't include the -1 terminator */ -#define NUM_MSS (ARRAY_SIZE(msstab) - 1) /* * Generate a syncookie. mssp points to the mss, which is returned @@ -169,10 +169,10 @@ __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp) tcp_synq_overflow(sk); - /* XXX sort msstab[] by probability? Binary search? */ - for (mssind = 0; mss > msstab[mssind + 1]; mssind++) - ; - *mssp = msstab[mssind] + 1; + 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); @@ -202,7 +202,7 @@ static inline int cookie_check(struct sk_buff *skb, __u32 cookie) jiffies / (HZ * 60), COUNTER_TRIES); - return mssind < NUM_MSS ? msstab[mssind] + 1 : 0; + return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0; } static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb, |