[PATCHv2 net-next 0/4] Small fix for TCP PMTU

Hi,

This patchset performs some small fix and enhancement
for current TCP PMTU as per RFC4821 with below changes:

Patch1/4: Set probe mss base to 1024 Bytes per RFC4821
Patch2/4: Do not double probe_size for each probing,
          use a simple binary search to gain maximum performance.
Patch3/4: When it comes to blackhole detection, shrink current
	  mss for next probing.
Patch4/4: Create a probe timer to detect enlarged path MTU.

Changelog:
v2:
   - Introduce sysctl_tcp_probe_threshold to control when
     probing will stop, as suggested by John Heffner.
   - Add patch3 to shrink current mss value for search low boundary.
   - Drop cannonical timer usages, implements pseudo timer based on
     32bits jiffies tcp_time_stamp, as suggested by Eric Dumazet.

Fan Du (4):
  ipv4: Raise tcp PMTU probe mss base size
  ipv4: Use binary search to choose tcp PMTU probe_size
  ipv4: shrink current mss for tcp PMTU blackhole detection
  ipv4: Create probe timer for tcp PMTU as per RFC4821

 include/net/inet_connection_sock.h |    2 +
 include/net/netns/ipv4.h           |    2 +
 include/net/tcp.h                  |    8 +++++-
 net/ipv4/sysctl_net_ipv4.c         |   14 ++++++++++
 net/ipv4/tcp_ipv4.c                |    2 +
 net/ipv4/tcp_output.c              |   50 +++++++++++++++++++++++++++++++++---
 net/ipv4/tcp_timer.c               |    8 +++--
 7 files changed, 78 insertions(+), 8 deletions(-)