Messages in this thread Patch in this message |  | | | Date | Wed, 31 Oct 2007 08:11:40 -0700 | | From | Greg KH <> | | Subject | [patch 12/26] : Fix TCP initial sequence number selection. |
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2.6.22-stable review patch. If anyone has any objections, please let us know.
------------------ From: Eric Dumazet <dada1@cosmosbay.com> 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>
--- drivers/char/random.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1550,11 +1550,13 @@ __u32 secure_tcp_sequence_number(__be32 * 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); -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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