diff options
author | Shmulik Ladkani <shmulik@metanetworks.com> | 2022-08-31 17:40:09 +0300 |
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committer | Daniel Borkmann <daniel@iogearbox.net> | 2022-09-02 16:20:55 +0300 |
commit | 44c51472bef83bb70b43e2f4b7a592096f32a855 (patch) | |
tree | 319b13744cf84c34d4bdb5caa6d87fb7206c998a /net | |
parent | dc84dbbcc97bfb47e0f2b175d816e601b2890c91 (diff) | |
download | linux-44c51472bef83bb70b43e2f4b7a592096f32a855.tar.xz |
bpf: Support getting tunnel flags
Existing 'bpf_skb_get_tunnel_key' extracts various tunnel parameters
(id, ttl, tos, local and remote) but does not expose ip_tunnel_info's
tun_flags to the BPF program.
It makes sense to expose tun_flags to the BPF program.
Assume for example multiple GRE tunnels maintained on a single GRE
interface in collect_md mode. The program expects origins to initiate
over GRE, however different origins use different GRE characteristics
(e.g. some prefer to use GRE checksum, some do not; some pass a GRE key,
some do not, etc..).
A BPF program getting tun_flags can therefore remember the relevant
flags (e.g. TUNNEL_CSUM, TUNNEL_SEQ...) for each initiating remote. In
the reply path, the program can use 'bpf_skb_set_tunnel_key' in order
to correctly reply to the remote, using similar characteristics, based
on the stored tunnel flags.
Introduce BPF_F_TUNINFO_FLAGS flag for bpf_skb_get_tunnel_key. If
specified, 'bpf_tunnel_key->tunnel_flags' is set with the tun_flags.
Decided to use the existing unused 'tunnel_ext' as the storage for the
'tunnel_flags' in order to avoid changing bpf_tunnel_key's layout.
Also, the following has been considered during the design:
1. Convert the "interesting" internal TUNNEL_xxx flags back to BPF_F_yyy
and place into the new 'tunnel_flags' field. This has 2 drawbacks:
- The BPF_F_yyy flags are from *set_tunnel_key* enumeration space,
e.g. BPF_F_ZERO_CSUM_TX. It is awkward that it is "returned" into
tunnel_flags from a *get_tunnel_key* call.
- Not all "interesting" TUNNEL_xxx flags can be mapped to existing
BPF_F_yyy flags, and it doesn't make sense to create new BPF_F_yyy
flags just for purposes of the returned tunnel_flags.
2. Place key.tun_flags into 'tunnel_flags' but mask them, keeping only
"interesting" flags. That's ok, but the drawback is that what's
"interesting" for my usecase might be limiting for other usecases.
Therefore I decided to expose what's in key.tun_flags *as is*, which seems
most flexible. The BPF user can just choose to ignore bits he's not
interested in. The TUNNEL_xxx are also UAPI, so no harm exposing them
back in the get_tunnel_key call.
Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220831144010.174110-1-shmulik.ladkani@gmail.com
Diffstat (limited to 'net')
-rw-r--r-- | net/core/filter.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 63e25d8ce501..74e2a4a0d747 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -4488,7 +4488,8 @@ BPF_CALL_4(bpf_skb_get_tunnel_key, struct sk_buff *, skb, struct bpf_tunnel_key void *to_orig = to; int err; - if (unlikely(!info || (flags & ~(BPF_F_TUNINFO_IPV6)))) { + if (unlikely(!info || (flags & ~(BPF_F_TUNINFO_IPV6 | + BPF_F_TUNINFO_FLAGS)))) { err = -EINVAL; goto err_clear; } @@ -4520,7 +4521,10 @@ set_compat: to->tunnel_id = be64_to_cpu(info->key.tun_id); to->tunnel_tos = info->key.tos; to->tunnel_ttl = info->key.ttl; - to->tunnel_ext = 0; + if (flags & BPF_F_TUNINFO_FLAGS) + to->tunnel_flags = info->key.tun_flags; + else + to->tunnel_ext = 0; if (flags & BPF_F_TUNINFO_IPV6) { memcpy(to->remote_ipv6, &info->key.u.ipv6.src, |