diff options
| author | Jesper Dangaard Brouer <brouer@redhat.com> | 2021-02-09 14:38:19 +0100 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2021-02-13 01:15:22 +0100 |
| commit | e1850ea9bd9eca3656820b4875967d6f9c11c237 (patch) | |
| tree | cdf5482ccdd7570d989bfd310e20c35508471bc3 /include/uapi | |
| parent | 2c0a10af688c02adcf127aad29e923e0056c6b69 (diff) | |
bpf: bpf_fib_lookup return MTU value as output when looked up
The BPF-helpers for FIB lookup (bpf_xdp_fib_lookup and bpf_skb_fib_lookup)
can perform MTU check and return BPF_FIB_LKUP_RET_FRAG_NEEDED. The BPF-prog
don't know the MTU value that caused this rejection.
If the BPF-prog wants to implement PMTU (Path MTU Discovery) (rfc1191) it
need to know this MTU value for the ICMP packet.
Patch change lookup and result struct bpf_fib_lookup, to contain this MTU
value as output via a union with 'tot_len' as this is the value used for
the MTU lookup.
V5:
- Fixed uninit value spotted by Dan Carpenter.
- Name struct output member mtu_result
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/161287789952.790810.13134700381067698781.stgit@firesoul
Diffstat (limited to 'include/uapi')
| -rw-r--r-- | include/uapi/linux/bpf.h | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 07cc2e404291..6b1f6058cccf 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2239,6 +2239,9 @@ union bpf_attr { * * > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the * packet is not forwarded or needs assist from full stack * + * If lookup fails with BPF_FIB_LKUP_RET_FRAG_NEEDED, then the MTU + * was exceeded and output params->mtu_result contains the MTU. + * * long bpf_sock_hash_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags) * Description * Add an entry to, or update a sockhash *map* referencing sockets. @@ -4990,9 +4993,13 @@ struct bpf_fib_lookup { __be16 sport; __be16 dport; - /* total length of packet from network header - used for MTU check */ - __u16 tot_len; + union { /* used for MTU check */ + /* input to lookup */ + __u16 tot_len; /* L3 length from network hdr (iph->tot_len) */ + /* output: MTU value */ + __u16 mtu_result; + }; /* input: L3 device index for lookup * output: device index from FIB lookup */ |