[Bug 230640] pf_map_addr operates on unlocked src_nodes and pools

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=230640

            Bug ID: 230640
           Summary: pf_map_addr operates on unlocked src_nodes and pools
           Product: Base System
           Version: 11.2-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: bugs at FreeBSD.org
          Reporter: vegeta at tuxpowered.net

Created attachment 196212
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=196212&action=edit
Fix locking issues around pf_map_addr.

I came across the following issues with pf_map_addr:

- It operates on unlocked src_nodes and I've seen kernel crashes attributable
to this.

- For route-to targets which specify outgoing interface, interface selection
happens outside of pf_map_addr and can be taken from different redirection
target than was used for IP address selection.

- Hash used for locking and unlocking src_node is calculated multiple times for
same src_node.

- Operations on rule->pool are unlocked, there even is a comment in code
mentioning circumstances where it can cause kernel crash.


I attached a patch addressing those issues. Please note it is early version, it
compiles, it runs, I'm not sure if it is really correct. The patch does the
following:

- Struct pf_pool has a lock now. Round-robin algorithm in pf_map_addr locks the
pool. Other algorithms don't do it, I don't think they need. Should we also
have table operations check this lock?

- pf_find_src_node does not manipulate src_node's state counter. It is a "find"
function so why would it manipulate other stuff? Also with new location of
sn->states++ removing of unused src_node in pf_create_state will work, I'm
pretty sure it was broken before.

- pf_insert_src_node returns locked. The lock is retained across
pf_create_state and pf_map_addr.

- pf_insert_src_node returns hash (row) of locked src_node. It is used later
for unlocking without recalculating the hash.

- Interface chosen by pf_map_addr is assigned to external variable from within
this function. Struct src_node stores the interface.

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