inet_diag: avoid cache line misses in inet_diag_bc_sk()

inet_diag_bc_sk() pulls five cache lines per socket,
while most filters only need the two first ones.

Add three booleans to struct inet_diag_dump_data,
that are selectively set if a filter needs specific socket fields.

- mark_needed       /* INET_DIAG_BC_MARK_COND present. */
- cgroup_needed     /* INET_DIAG_BC_CGROUP_COND present. */
- userlocks_needed  /* INET_DIAG_BC_AUTO present. */

This removes millions of cache lines misses per ss invocation
when simple filters are specified on busy servers.

offsetof(struct sock, sk_userlocks) = 0xf3
offsetof(struct sock, sk_mark) = 0x20c
offsetof(struct sock, sk_cgrp_data) = 0x298

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250828102738.2065992-6-edumazet@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>