[PATCH] NET: SRv6: seg6_local: Fixed SRH processing when segments left is 0

[Suprit Japagal]

From: "Suprit.Japagal" <suprit.japa...@gmail.com>

According to the standard IETF RFC 8754, section 4.3.1.1
(https://tools.ietf.org/html/rfc8754#section-4.3.1.1)
When the segments left in SRH equals to 0, proceed to process the
next header in the packet, whose type is identified by the
Next header field of the routing header.

Signed-off-by: Suprit.Japagal <suprit.japa...@gmail.com>
---
 net/ipv6/seg6_local.c | 54 +++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 48 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index b07f7c1..b17f9dc 100644
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -273,11 +273,25 @@ static int input_action_end(struct sk_buff *skb, struct 
seg6_local_lwt *slwt)
 {
        struct ipv6_sr_hdr *srh;
 
-       srh = get_and_validate_srh(skb);
+       srh = get_srh(skb);
        if (!srh)
                goto drop;
 
-       advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
+#ifdef CONFIG_IPV6_SEG6_HMAC
+       if (srh->segments_left > 0)
+               if (!seg6_hmac_validate_skb(skb))
+                       goto drop;
+#endif
+
+       if (srh->segments_left == 0) {
+               if (!decap_and_validate(skb, srh->nexthdr))
+                       goto drop;
+
+               if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
+                       goto drop;
+       } else {
+               advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
+       }
 
        seg6_lookup_nexthop(skb, NULL, 0);
 
@@ -293,11 +307,25 @@ static int input_action_end_x(struct sk_buff *skb, struct 
seg6_local_lwt *slwt)
 {
        struct ipv6_sr_hdr *srh;
 
-       srh = get_and_validate_srh(skb);
+       srh = get_srh(skb);
        if (!srh)
                goto drop;
 
-       advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
+#ifdef CONFIG_IPV6_SEG6_HMAC
+       if (srh->segments_left > 0)
+               if (!seg6_hmac_validate_skb(skb))
+                       goto drop;
+#endif
+
+       if (srh->segments_left == 0) {
+               if (!decap_and_validate(skb, srh->nexthdr))
+                       goto drop;
+
+               if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
+                       goto drop;
+       } else {
+               advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
+       }
 
        seg6_lookup_nexthop(skb, &slwt->nh6, 0);
 
@@ -312,11 +340,25 @@ static int input_action_end_t(struct sk_buff *skb, struct 
seg6_local_lwt *slwt)
 {
        struct ipv6_sr_hdr *srh;
 
-       srh = get_and_validate_srh(skb);
+       srh = get_srh(skb);
        if (!srh)
                goto drop;
 
-       advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
+#ifdef CONFIG_IPV6_SEG6_HMAC
+       if (srh->segments_left > 0)
+               if (!seg6_hmac_validate_skb(skb))
+                       goto drop;
+#endif
+
+       if (srh->segments_left == 0) {
+               if (!decap_and_validate(skb, srh->nexthdr))
+                       goto drop;
+
+               if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
+                       goto drop;
+       } else {
+               advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
+       }
 
        seg6_lookup_nexthop(skb, NULL, slwt->table);
 
-- 
2.9.3