summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorEric Dumazet <dada1@cosmosbay.com>2007-10-10 03:28:33 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2007-11-02 08:44:11 -0700
commitdec0da2c0b439daf394957660e62824987f9b021 (patch)
tree44a48c2e35f7e04cf87b113db2c58bb86720571a
parent55d0058fe82cade2896d316952341c64d7dfa7c9 (diff)
Fix TCP initial sequence number selection.
changeset 162f6690a65075b49f242d3c8cdb5caaa959a060 in mainline. TCP V4 sequence numbers are 32bits, and RFC 793 assumed a 250 KHz clock. In order to follow network speed increase, we can use a faster clock, but we should limit this clock so that the delay between two rollovers is greater than MSL (TCP Maximum Segment Lifetime : 2 minutes) Choosing a 64 nsec clock should be OK, since the rollovers occur every 274 seconds. Problem spotted by Denys Fedoryshchenko [ This bug was introduced by f85958151900f9d30fa5ff941b0ce71eaa45a7de ] Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/char/random.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 397c714cf2ba..af274e5a25ee 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1550,11 +1550,13 @@ __u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
* As close as possible to RFC 793, which
* suggests using a 250 kHz clock.
* Further reading shows this assumes 2 Mb/s networks.
- * For 10 Gb/s Ethernet, a 1 GHz clock is appropriate.
- * That's funny, Linux has one built in! Use it!
- * (Networks are faster now - should this be increased?)
+ * For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
+ * For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but
+ * we also need to limit the resolution so that the u32 seq
+ * overlaps less than one time per MSL (2 minutes).
+ * Choosing a clock of 64 ns period is OK. (period of 274 s)
*/
- seq += ktime_get_real().tv64;
+ seq += ktime_get_real().tv64 >> 6;
#if 0
printk("init_seq(%lx, %lx, %d, %d) = %d\n",
saddr, daddr, sport, dport, seq);