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authorJesper Dangaard Brouer <brouer@redhat.com>2021-02-09 14:38:19 +0100
committerDaniel Borkmann <daniel@iogearbox.net>2021-02-13 01:15:22 +0100
commite1850ea9bd9eca3656820b4875967d6f9c11c237 (patch)
treecdf5482ccdd7570d989bfd310e20c35508471bc3 /tools
parent2c0a10af688c02adcf127aad29e923e0056c6b69 (diff)
downloadlinux-e1850ea9bd9eca3656820b4875967d6f9c11c237.tar.bz2
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 'tools')
-rw-r--r--tools/include/uapi/linux/bpf.h11
1 files changed, 9 insertions, 2 deletions
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 07cc2e404291..6b1f6058cccf 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/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
*/