ipv6: sr: add support for encapsulation of L2 frames

This patch implements the L2 frame encapsulation mechanism, referred to
as T.Encaps.L2 in the SRv6 specifications [1].

A new type of SRv6 tunnel mode is added (SEG6_IPTUN_MODE_L2ENCAP). It only
accepts packets with an existing MAC header (i.e., it will not work for
locally generated packets). The resulting packet looks like IPv6 -> SRH ->
Ethernet -> original L3 payload. The next header field of the SRH is set to
NEXTHDR_NONE.

[1] https://tools.ietf.org/html/draft-filsfils-spring-srv6-network-programming-01

Signed-off-by: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/seg6_iptunnel.h b/include/uapi/linux/seg6_iptunnel.h
index b6e5a0a..b23df9f 100644 (file)
--- a/include/uapi/linux/seg6_iptunnel.h
+++ b/include/uapi/linux/seg6_iptunnel.h
@@ -33,16 +33,26 @@ struct seg6_iptunnel_encap {
 enum {
        SEG6_IPTUN_MODE_INLINE,
        SEG6_IPTUN_MODE_ENCAP,
+       SEG6_IPTUN_MODE_L2ENCAP,
 };
 
 #ifdef __KERNEL__
 
 static inline size_t seg6_lwt_headroom(struct seg6_iptunnel_encap *tuninfo)
 {
-       int encap = (tuninfo->mode == SEG6_IPTUN_MODE_ENCAP);
-
-       return ((tuninfo->srh->hdrlen + 1) << 3) +
-              (encap * sizeof(struct ipv6hdr));
+       int head = 0;
+
+       switch (tuninfo->mode) {
+       case SEG6_IPTUN_MODE_INLINE:
+               break;
+       case SEG6_IPTUN_MODE_ENCAP:
+               head = sizeof(struct ipv6hdr);
+               break;
+       case SEG6_IPTUN_MODE_L2ENCAP:
+               return 0;
+       }
+
+       return ((tuninfo->srh->hdrlen + 1) << 3) + head;
 }
 
 #endif

diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c
index 5bec781..bd6cc68 100644 (file)
--- a/net/ipv6/seg6_iptunnel.c
+++ b/net/ipv6/seg6_iptunnel.c
@@ -240,6 +240,22 @@ static int seg6_do_srh(struct sk_buff *skb)
 
                skb->protocol = htons(ETH_P_IPV6);
                break;
+       case SEG6_IPTUN_MODE_L2ENCAP:
+               if (!skb_mac_header_was_set(skb))
+                       return -EINVAL;
+
+               if (pskb_expand_head(skb, skb->mac_len, 0, GFP_ATOMIC) < 0)
+                       return -ENOMEM;
+
+               skb_mac_header_rebuild(skb);
+               skb_push(skb, skb->mac_len);
+
+               err = seg6_do_srh_encap(skb, tinfo->srh, NEXTHDR_NONE);
+               if (err)
+                       return err;
+
+               skb->protocol = htons(ETH_P_IPV6);
+               break;
        }
 
        ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
@@ -386,6 +402,8 @@ static int seg6_build_state(struct nlattr *nla,
                break;
        case SEG6_IPTUN_MODE_ENCAP:
                break;
+       case SEG6_IPTUN_MODE_L2ENCAP:
+               break;
        default:
                return -EINVAL;
        }
@@ -409,8 +427,11 @@ static int seg6_build_state(struct nlattr *nla,
        memcpy(&slwt->tuninfo, tuninfo, tuninfo_len);
 
        newts->type = LWTUNNEL_ENCAP_SEG6;
-       newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT |
-                       LWTUNNEL_STATE_INPUT_REDIRECT;
+       newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
+
+       if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP)
+               newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
+
        newts->headroom = seg6_lwt_headroom(tuninfo);
 
        *ts = newts;