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syncookies: update mss tables 

- ipv6 msstab: account for ipv6 header size
- ipv4 msstab: add mss for Jumbograms.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal 2010-06-03 00:43:57 +00:00 committed by David S. Miller
parent af9b473857
commit 5918e2fb90
2 changed files with 34 additions and 43 deletions
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38
net/ipv4/syncookies.c
View File

@ -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,

39
net/ipv6/syncookies.c
View File

@ -27,28 +27,17 @@ extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
#define COOKIEBITS 24 /* Upper bits store count */
#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
/*
* 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.
*
* Taken directly from ipv4 implementation.
* Should this list be modified for ipv6 use or is it close enough?
* rfc 2460 8.3 suggests mss values 20 bytes less than ipv4 counterpart
*/
/* 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,
1280 - 60,
1480 - 60,
1500 - 60,
4460 - 60,
9000 - 60,
};
/* The number doesn't include the -1 terminator */
#define NUM_MSS (ARRAY_SIZE(msstab) - 1)
/*
* This (misnamed) value is the age of syncookie which is permitted.
@ -134,9 +123,11 @@ __u32 cookie_v6_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp)
tcp_synq_overflow(sk);
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);
@ -154,7 +145,7 @@ static inline int cookie_check(struct sk_buff *skb, __u32 cookie)
th->source, th->dest, seq,
jiffies / (HZ * 60), COUNTER_TRIES);
return mssind < NUM_MSS ? msstab[mssind] + 1 : 0;
return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
}
struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)