flow: fix podman issue #25959

While running piHole using podman, traffic can trigger the following
assert:

ASSSERTION FAILED in flow_alloc (flow.c:521): flow->f.state == FLOW_STATE_FREE

Backtrace shows that this happens in flow_defer_handler():

    #4  0x00005610d6f5b481 flow_alloc (passt + 0xb481)
    #5  0x00005610d6f74f86 udp_flow_from_sock (passt + 0x24f86)
    #6  0x00005610d6f737c3 udp_sock_fwd (passt + 0x237c3)
    #7  0x00005610d6f74c07 udp_flush_flow (passt + 0x24c07)
    #8  0x00005610d6f752c2 udp_flow_defer (passt + 0x252c2)
    #9  0x00005610d6f5bce1 flow_defer_handler (passt + 0xbce1)

We are trying to allocate a new flow inside the loop freeing them.

Inside the loop free_head points to the first free flow entry in the
current cluster. But if we allocate a new entry during the loop,
free_head is not updated and can point now to the entry we have just
allocated.

We can fix the problem by spliting the loop in two parts:
- first part where we can close some of them and allocate some new
  flow entries,
- second part where we free the entries closed in the previous loop
  and we aggregate the free entries to merge consecutive the clusters.

Reported-by: Martin Rijntjes <bugs@air-global.nl>
Link: https://github.com/containers/podman/issues/25959
Fixes: 9725e7988837 ("udp_flow: Don't discard packets that arrive between bind() and connect()")
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

0 files changed, 0 insertions, 0 deletions