[net-next v4] seg6: using DSCP of inner IPv4 packets

[Ahmed Abdelsalam]

This patch allows copying the DSCP from inner IPv4 header to the
outer IPv6 header, when doing SRv6 Encapsulation.

This allows forwarding packet across the SRv6 fabric based on their
original traffic class.

Signed-off-by: Ahmed Abdelsalam <ahabdels@xxxxxxxxx>
---
 net/ipv6/seg6_iptunnel.c | 36 +++++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 17 deletions(-)

diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c
index 897fa59c47de..7eaa7adc296b 100644
--- a/net/ipv6/seg6_iptunnel.c
+++ b/net/ipv6/seg6_iptunnel.c
@@ -104,8 +104,7 @@ static void set_tun_src(struct net *net, struct net_device *dev,
 }
 
 /* Compute flowlabel for outer IPv6 header */
-static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb,
-				  struct ipv6hdr *inner_hdr)
+static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb)
 {
 	int do_flowlabel = net->ipv6.sysctl.seg6_flowlabel;
 	__be32 flowlabel = 0;
@@ -116,7 +115,7 @@ static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb,
 		hash = rol32(hash, 16);
 		flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK;
 	} else if (!do_flowlabel && skb->protocol == htons(ETH_P_IPV6)) {
-		flowlabel = ip6_flowlabel(inner_hdr);
+		flowlabel = ip6_flowlabel(ipv6_hdr(skb));
 	}
 	return flowlabel;
 }
@@ -130,6 +129,7 @@ int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)
 	struct ipv6_sr_hdr *isrh;
 	int hdrlen, tot_len, err;
 	__be32 flowlabel;
+	u8 tos = 0, hop_limit;
 
 	hdrlen = (osrh->hdrlen + 1) << 3;
 	tot_len = hdrlen + sizeof(*hdr);
@@ -138,30 +138,32 @@ int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)
 	if (unlikely(err))
 		return err;
 
-	inner_hdr = ipv6_hdr(skb);
-	flowlabel = seg6_make_flowlabel(net, skb, inner_hdr);
-
-	skb_push(skb, tot_len);
-	skb_reset_network_header(skb);
-	skb_mac_header_rebuild(skb);
-	hdr = ipv6_hdr(skb);
-
 	/* inherit tc, flowlabel and hlim
 	 * hlim will be decremented in ip6_forward() afterwards and
 	 * decapsulation will overwrite inner hlim with outer hlim
 	 */
 
+	flowlabel = seg6_make_flowlabel(net, skb);
+	hop_limit = ip6_dst_hoplimit(skb_dst(skb));
+
 	if (skb->protocol == htons(ETH_P_IPV6)) {
-		ip6_flow_hdr(hdr, ip6_tclass(ip6_flowinfo(inner_hdr)),
-			     flowlabel);
-		hdr->hop_limit = inner_hdr->hop_limit;
+		inner_hdr = ipv6_hdr(skb);
+		hop_limit = inner_hdr->hop_limit;
+		tos = ip6_tclass(ip6_flowinfo(inner_hdr));
+	} else if (skb->protocol == htons(ETH_P_IP)) {
+		tos = ip_hdr(skb)->tos;
+		memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
 	} else {
-		ip6_flow_hdr(hdr, 0, flowlabel);
-		hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb));
-
 		memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
 	}
 
+	skb_push(skb, tot_len);
+	skb_reset_network_header(skb);
+	skb_mac_header_rebuild(skb);
+
+	hdr = ipv6_hdr(skb);
+	ip6_flow_hdr(hdr, tos, flowlabel);
+	hdr->hop_limit = hop_limit;
 	hdr->nexthdr = NEXTHDR_ROUTING;
 
 	isrh = (void *)hdr + sizeof(*hdr);
-- 
2.17.1