ip6_tunnel, ip6_gre: fix setting of DSCP on encapsulated packets

[ Upstream commit 0e9a709560dbcfbace8bf4019dc5298619235891 ]

This fix addresses two problems in the way the DSCP field is formulated
 on the encapsulating header of IPv6 tunnels.
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=195661

1) The IPv6 tunneling code was manipulating the DSCP field of the
 encapsulating packet using the 32b flowlabel. Since the flowlabel is
 only the lower 20b it was incorrect to assume that the upper 12b
 containing the DSCP and ECN fields would remain intact when formulating
 the encapsulating header. This fix handles the 'inherit' and
 'fixed-value' DSCP cases explicitly using the extant dsfield u8 variable.

2) The use of INET_ECN_encapsulate(0, dsfield) in ip6_tnl_xmit was
 incorrect and resulted in the DSCP value always being set to 0.

Commit 90427ef5d2a4 ("ipv6: fix flow labels when the traffic class
 is non-0") caused the regression by masking out the flowlabel
 which exposed the incorrect handling of the DSCP portion of the
 flowlabel in ip6_tunnel and ip6_gre.

Fixes: 90427ef5d2a4 ("ipv6: fix flow labels when the traffic class is non-0")
Signed-off-by: Peter Dawson <peter.a.dawson@boeing.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 20 insertions, 14 deletions

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index a5fdc1aa7a9a..d2844ee469cb 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -542,11 +542,10 @@ static inline int ip6gre_xmit_ipv4(struct sk_buff *skb, struct net_device *dev)
 
 	memcpy(&fl6, &t->fl.u.ip6, sizeof(fl6));
 
-	dsfield = ipv4_get_dsfield(iph);
-
 	if (t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS)
-		fl6.flowlabel |= htonl((__u32)iph->tos << IPV6_TCLASS_SHIFT)
-					  & IPV6_TCLASS_MASK;
+		dsfield = ipv4_get_dsfield(iph);
+	else
+		dsfield = ip6_tclass(t->parms.flowinfo);
 	if (t->parms.flags & IP6_TNL_F_USE_ORIG_FWMARK)
 		fl6.flowi6_mark = skb->mark;
 
@@ -599,9 +598,11 @@ static inline int ip6gre_xmit_ipv6(struct sk_buff *skb, struct net_device *dev)
 
 	memcpy(&fl6, &t->fl.u.ip6, sizeof(fl6));
 
-	dsfield = ipv6_get_dsfield(ipv6h);
 	if (t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS)
-		fl6.flowlabel |= (*(__be32 *) ipv6h & IPV6_TCLASS_MASK);
+		dsfield = ipv6_get_dsfield(ipv6h);
+	else
+		dsfield = ip6_tclass(t->parms.flowinfo);
+
 	if (t->parms.flags & IP6_TNL_F_USE_ORIG_FLOWLABEL)
 		fl6.flowlabel |= ip6_flowlabel(ipv6h);
 	if (t->parms.flags & IP6_TNL_F_USE_ORIG_FWMARK)
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 63fad2467a7e..1fc9daa7b1d6 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1196,7 +1196,7 @@ route_lookup:
 	skb_push(skb, sizeof(struct ipv6hdr));
 	skb_reset_network_header(skb);
 	ipv6h = ipv6_hdr(skb);
-	ip6_flow_hdr(ipv6h, INET_ECN_encapsulate(0, dsfield),
+	ip6_flow_hdr(ipv6h, dsfield,
 		     ip6_make_flowlabel(net, skb, fl6->flowlabel, true, fl6));
 	ipv6h->hop_limit = hop_limit;
 	ipv6h->nexthdr = proto;
@@ -1231,8 +1231,6 @@ ip4ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (tproto != IPPROTO_IPIP && tproto != 0)
 		return -1;
 
-	dsfield = ipv4_get_dsfield(iph);
-
 	if (t->parms.collect_md) {
 		struct ip_tunnel_info *tun_info;
 		const struct ip_tunnel_key *key;
@@ -1246,6 +1244,7 @@ ip4ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 		fl6.flowi6_proto = IPPROTO_IPIP;
 		fl6.daddr = key->u.ipv6.dst;
 		fl6.flowlabel = key->label;
+		dsfield = ip6_tclass(key->label);
 	} else {
 		if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
 			encap_limit = t->parms.encap_limit;
@@ -1254,8 +1253,9 @@ ip4ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 		fl6.flowi6_proto = IPPROTO_IPIP;
 
 		if (t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS)
-			fl6.flowlabel |= htonl((__u32)iph->tos << IPV6_TCLASS_SHIFT)
-					 & IPV6_TCLASS_MASK;
+			dsfield = ipv4_get_dsfield(iph);
+		else
+			dsfield = ip6_tclass(t->parms.flowinfo);
 		if (t->parms.flags & IP6_TNL_F_USE_ORIG_FWMARK)
 			fl6.flowi6_mark = skb->mark;
 	}
@@ -1263,6 +1263,8 @@ ip4ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6))
 		return -1;
 
+	dsfield = INET_ECN_encapsulate(dsfield, ipv4_get_dsfield(iph));
+
 	skb_set_inner_ipproto(skb, IPPROTO_IPIP);
 
 	err = ip6_tnl_xmit(skb, dev, dsfield, &fl6, encap_limit, &mtu,
@@ -1296,8 +1298,6 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 	    ip6_tnl_addr_conflict(t, ipv6h))
 		return -1;
 
-	dsfield = ipv6_get_dsfield(ipv6h);
-
 	if (t->parms.collect_md) {
 		struct ip_tunnel_info *tun_info;
 		const struct ip_tunnel_key *key;
@@ -1311,6 +1311,7 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 		fl6.flowi6_proto = IPPROTO_IPV6;
 		fl6.daddr = key->u.ipv6.dst;
 		fl6.flowlabel = key->label;
+		dsfield = ip6_tclass(key->label);
 	} else {
 		offset = ip6_tnl_parse_tlv_enc_lim(skb, skb_network_header(skb));
 		/* ip6_tnl_parse_tlv_enc_lim() might have reallocated skb->head */
@@ -1333,7 +1334,9 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 		fl6.flowi6_proto = IPPROTO_IPV6;
 
 		if (t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS)
-			fl6.flowlabel |= (*(__be32 *)ipv6h & IPV6_TCLASS_MASK);
+			dsfield = ipv6_get_dsfield(ipv6h);
+		else
+			dsfield = ip6_tclass(t->parms.flowinfo);
 		if (t->parms.flags & IP6_TNL_F_USE_ORIG_FLOWLABEL)
 			fl6.flowlabel |= ip6_flowlabel(ipv6h);
 		if (t->parms.flags & IP6_TNL_F_USE_ORIG_FWMARK)
@@ -1343,6 +1346,8 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6))
 		return -1;
 
+	dsfield = INET_ECN_encapsulate(dsfield, ipv6_get_dsfield(ipv6h));
+
 	skb_set_inner_ipproto(skb, IPPROTO_IPV6);
 
 	err = ip6_tnl_xmit(skb, dev, dsfield, &fl6, encap_limit, &mtu,