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>
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index c9dac86..a7cbcc4 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -138,23 +138,23 @@
}
/*
- * 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 @@
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 @@
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,