bpf: add End.DT6 action to bpf_lwt_seg6_action helper

The seg6local LWT provides the End.DT6 action, which allows to
decapsulate an outer IPv6 header containing a Segment Routing Header
(SRH), full specification is available here:

https://tools.ietf.org/html/draft-filsfils-spring-srv6-network-programming-05

This patch adds this action now to the seg6local BPF
interface. Since it is not mandatory that the inner IPv6 header also
contains a SRH, seg6_bpf_srh_state has been extended with a pointer to
a possible SRH of the outermost IPv6 header. This helps assessing if the
validation must be triggered or not, and avoids some calls to
ipv6_find_hdr.

v3: s/1/true, s/0/false for boolean values
v2: - changed true/false -> 1/0
    - preempt_enable no longer called in first conditional block

Signed-off-by: Mathieu Xhonneux <m.xhonneux@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/include/net/seg6_local.h b/include/net/seg6_local.h
index 661fd5b4d3e0..08359e2d8b35 100644
--- a/include/net/seg6_local.h
+++ b/include/net/seg6_local.h
@@ -21,10 +21,12 @@
 
 extern int seg6_lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
 			       u32 tbl_id);
+extern bool seg6_bpf_has_valid_srh(struct sk_buff *skb);
 
 struct seg6_bpf_srh_state {
-	bool valid;
+	struct ipv6_sr_hdr *srh;
 	u16 hdrlen;
+	bool valid;
 };
 
 DECLARE_PER_CPU(struct seg6_bpf_srh_state, seg6_bpf_srh_states);