linux-kernel - [PATCH] seg6: using DSCP of inner IPv4 packets

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Date:   Tue,  4 Aug 2020 07:40:30 +0000
From:   Ahmed Abdelsalam <ahabdels@...il.com>
To:     davem@...emloft.net, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        andrea.mayer@...roma2.it
Cc:     Ahmed Abdelsalam <ahabdels@...il.com>
Subject: [PATCH] seg6: using DSCP of inner IPv4 packets

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@...il.com>
---
 net/ipv6/seg6_iptunnel.c | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c
index e0e9f48ab14f..12fb32ca64f7 100644
--- a/net/ipv6/seg6_iptunnel.c
+++ b/net/ipv6/seg6_iptunnel.c
@@ -87,8 +87,7 @@ 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;
@@ -99,7 +98,7 @@ 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;
 }
@@ -109,10 +108,11 @@ int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)
 {
 	struct dst_entry *dst = skb_dst(skb);
 	struct net *net = dev_net(dst->dev);
-	struct ipv6hdr *hdr, *inner_hdr;
 	struct ipv6_sr_hdr *isrh;
 	int hdrlen, tot_len, err;
+	struct ipv6hdr *hdr;
 	__be32 flowlabel;
+	u8 tos = 0;
 
 	hdrlen = (osrh->hdrlen + 1) << 3;
 	tot_len = hdrlen + sizeof(*hdr);
@@ -121,31 +121,31 @@ 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);
+
 	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;
+		tos = ip6_tclass(ip6_flowinfo(ipv6_hdr(skb)));
+	} 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->nexthdr = NEXTHDR_ROUTING;
+	hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb));
 
 	isrh = (void *)hdr + sizeof(*hdr);
 	memcpy(isrh, osrh, hdrlen);
-- 
2.17.1