linux.git/net/ipv4/tcp_timer.c, branch v2.6.32

Revert Backoff [v3]: Calculate TCP's connection close threshold as a time value.

2009-09-01T09:45:47+00:00

RFC 1122 specifies two threshold values R1 and R2 for connection timeouts,
which may represent a number of allowed retransmissions or a timeout value.
Currently linux uses sysctl_tcp_retries{1,2} to specify the thresholds
in number of allowed retransmissions.

For any desired threshold R2 (by means of time) one can specify tcp_retries2
(by means of number of retransmissions) such that TCP will not time out
earlier than R2. This is the case, because the RTO schedule follows a fixed
pattern, namely exponential backoff.

However, the RTO behaviour is not predictable any more if RTO backoffs can be
reverted, as it is the case in the draft
"Make TCP more Robust to Long Connectivity Disruptions"
(http://tools.ietf.org/html/draft-zimmermann-tcp-lcd).

In the worst case TCP would time out a connection after 3.2 seconds, if the
initial RTO equaled MIN_RTO and each backoff has been reverted.

This patch introduces a function retransmits_timed_out(N),
which calculates the timeout of a TCP connection, assuming an initial
RTO of MIN_RTO and N unsuccessful, exponentially backed-off retransmissions.

Whenever timeout decisions are made by comparing the retransmission counter
to some value N, this function can be used, instead.

The meaning of tcp_retries2 will be changed, as many more RTO retransmissions
can occur than the value indicates. However, it yields a timeout which is
similar to the one of an unpatched, exponentially backing off TCP in the same
scenario. As no application could rely on an RTO greater than MIN_RTO, there
should be no risk of a regression.

Signed-off-by: Damian Lukowski 
Acked-by: Ilpo Järvinen 
Signed-off-by: David S. Miller

Revert Backoff [v3]: Revert RTO on ICMP destination unreachable

2009-09-01T09:45:42+00:00

Here, an ICMP host/network unreachable message, whose payload fits to
TCP's SND.UNA, is taken as an indication that the RTO retransmission has
not been lost due to congestion, but because of a route failure
somewhere along the path.
With true congestion, a router won't trigger such a message and the
patched TCP will operate as standard TCP.

This patch reverts one RTO backoff, if an ICMP host/network unreachable
message, whose payload fits to TCP's SND.UNA, arrives.
Based on the new RTO, the retransmission timer is reset to reflect the
remaining time, or - if the revert clocked out the timer - a retransmission
is sent out immediately.
Backoffs are only reverted, if TCP is in RTO loss recovery, i.e. if
there have been retransmissions and reversible backoffs, already.

Changes from v2:
1) Renaming of skb in tcp_v4_err() moved to another patch.
2) Reintroduced tcp_bound_rto() and __tcp_set_rto().
3) Fixed code comments.

Signed-off-by: Damian Lukowski 
Acked-by: Ilpo Järvinen 
Signed-off-by: David S. Miller

tcp: keepalive cleanups

2009-08-29T06:48:54+00:00

Introduce keepalive_probes(tp) helper, and use it, like 
keepalive_time_when(tp) and keepalive_intvl_when(tp)

Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

tcp: cleanup ca_state mess in tcp_timer

2009-03-02T11:00:13+00:00

Redundant checks made indentation impossible to follow.
However, it might be useful to make this ca_state+is_sack
indexed array.

Signed-off-by: Ilpo Järvinen 
Signed-off-by: David S. Miller

tcp: Stop scaring users with "treason uncloaked!"

2008-12-19T06:27:42+00:00

The original message was unhelpful and extremely alarming to our poor
users, despite its charm. Make it less frightening.

Signed-off-by: Matt Mackall 
Signed-off-by: David S. Miller

net: Use a percpu_counter for orphan_count

2008-11-26T05:17:14+00:00

Instead of using one atomic_t per protocol, use a percpu_counter
for "orphan_count", to reduce cache line contention on
heavy duty network servers. 

Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

net: clean up net/ipv4/ip_fragment.c tcp_timer.c ip_input.c

2008-11-03T10:47:38+00:00

Signed-off-by: Jianjun Kong 
Signed-off-by: David S. Miller

net: replace NIPQUAD() in net/ipv4/ net/ipv6/

2008-10-31T07:53:57+00:00

Using NIPQUAD() with NIPQUAD_FMT, %d.%d.%d.%d or %u.%u.%u.%u
can be replaced with %pI4

Signed-off-by: Harvey Harrison 
Signed-off-by: David S. Miller

net: replace %p6 with %pI6

2008-10-29T19:52:50+00:00

Signed-off-by: Harvey Harrison 
Signed-off-by: David S. Miller

net: replace uses of NIP6_FMT with %p6

2008-10-29T06:02:31+00:00

Signed-off-by: Harvey Harrison 
Signed-off-by: David S. Miller