Re: [PATCH net-next v2 0/3] Report netns cookie in FIB lookup tracepoints

[Paolo Abeni <pabeni@redhat.com>]

On 10/8/26 15:31, Ido Schimmel wrote:
> The fib:fib_table_lookup and fib6:fib6_table_lookup tracepoints do not
> report the network namespace in which the lookup was performed, so
> lookups performed in different namespaces cannot be told apart. The
> recorded PID does not help either, as lookups in the receive path are
> performed in softIRQ context.
> 
> This is a problem, for example, for netns-aware tracers [1] and
> multi-ASIC systems where each ASIC and its ports reside in a separate
> network namespace.
> 
> This patchset reports the network namespace cookie in both tracepoints,
> as commit 27cb3de7f43a ("net: add net cookie for net device trace
> events") did for the net device tracepoints. This allows filtering
> lookups performed in a specific network namespace, for example:
> 
>   # perf record -a -e fib:fib_table_lookup --filter 'net_cookie == 12'
> 
> The cookie of a given network namespace can be retrieved using "ip netns
> cookie" [2].
> 
> Patch #1 reports the cookie in the IPv6 tracepoint, which is already
> passed the network namespace.
> 
> Patch #2 passes the network namespace to fib_table_lookup() and from
> there to the IPv4 tracepoint.
> 
> Patch #3 reports the cookie in the IPv4 tracepoint.
Not intended to block the above (could be eventually a follow-up), but
I'm wondering if you have considered adding a `net` (or net_cookie) field
to the fib_table struct instead of passing the net as an additional argument
to the lookup functions - AFAICS the latter are also called in critical
path and the additional arg could be unneeded (very small) overhead.

/P