[net,v2,0/3] Avoid TCP resets when using ECMP for load-balancing between multiple servers.

Message

Sriram Yagnaraman Aug. 25, 2023, 9:08 a.m. UTC

All packets in the same flow (L3/L4 depending on multipath hash policy)
should be directed to the same target, but after [0]/[1] we see stray
packets directed towards other targets. This, for instance, causes RST
to be sent on TCP connections.

The first two patches solve the problem by ignoring route hints for
destinations that are part of multipath group, by using new SKB flags
for IPv4 and IPv6. The third patch is a selftest that tests the
scenario.

Thanks to Ido, for reviewing and suggesting a way forward in [2] and
also suggesting how to write a selftest for this.

v1->v2:
- Update to commit messages describing the solution (Ido Schimmel)
- Use perf stat to count fib table lookups in selftest (Ido Schimmel)


Sriram Yagnaraman (3):
  ipv4: ignore dst hint for multipath routes
  ipv6: ignore dst hint for multipath routes
  selftests: forwarding: Add test for load-balancing between multiple
    servers

 include/linux/ipv6.h                          |   1 +
 include/net/ip.h                              |   1 +
 net/ipv4/ip_input.c                           |   3 +-
 net/ipv4/route.c                              |   1 +
 net/ipv6/ip6_input.c                          |   3 +-
 net/ipv6/route.c                              |   2 +
 .../testing/selftests/net/forwarding/Makefile |   1 +
 tools/testing/selftests/net/forwarding/lib.sh |   5 +
 .../net/forwarding/router_multipath_vip.sh    | 255 ++++++++++++++++++
 9 files changed, 270 insertions(+), 2 deletions(-)
 create mode 100755 tools/testing/selftests/net/forwarding/router_multipath_vip.sh