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authorFlorian Westphal <fw@strlen.de>2010-06-03 04:43:57 +0400
committerDavid S. Miller <davem@davemloft.net>2010-06-05 13:23:15 +0400
commit5918e2fb9035b35164002c3a268feaf70b7c04d5 (patch)
tree3a785e4b13971d9b9e9098a339ad005364949852
parentaf9b4738574b46025de7ccbe75c7b24fd8914379 (diff)
downloadlinux-5918e2fb9035b35164002c3a268feaf70b7c04d5.tar.xz
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>
-rw-r--r--net/ipv4/syncookies.c38
-rw-r--r--net/ipv6/syncookies.c39
2 files changed, 34 insertions, 43 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,
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 9fcb3ec7c838..70d330f8c990 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -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)