udp6: Use Segment Routing Header for dest address if present

When finding the socket to report an error on, if the invoking packet
is using Segment Routing, the IPv6 destination address is that of an
intermediate router, not the end destination. Extract the ultimate
destination address from the segment address.

This change allows traceroute to function in the presence of Segment
Routing.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/seg6.h b/include/net/seg6.h
index 02b0cd305787656f372a2af8d414d3c9b6f46fb8..af668f17b3988d890fed907a22339cfc1d3fd25c 100644 (file)
--- a/include/net/seg6.h
+++ b/include/net/seg6.h
@@ -65,4 +65,23 @@ extern int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh,
 extern int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh);
 extern int seg6_lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
                               u32 tbl_id);
+
+/* If the packet which invoked an ICMP error contains an SRH return
+ * the true destination address from within the SRH, otherwise use the
+ * destination address in the IP header.
+ */
+static inline const struct in6_addr *seg6_get_daddr(struct sk_buff *skb,
+                                                   struct inet6_skb_parm *opt)
+{
+       struct ipv6_sr_hdr *srh;
+
+       if (opt->flags & IP6SKB_SEG6) {
+               srh = (struct ipv6_sr_hdr *)(skb->data + opt->srhoff);
+               return  &srh->segments[0];
+       }
+
+       return NULL;
+}
+
+
 #endif

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 8cde9efd79198adc1a83260d0ffad21ee3b185ae..a0871c212741c51a285185b6c28fa2627fc35fb6 100644 (file)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -40,6 +40,7 @@
 #include <net/transp_v6.h>
 #include <net/ip6_route.h>
 #include <net/raw.h>
+#include <net/seg6.h>
 #include <net/tcp_states.h>
 #include <net/ip6_checksum.h>
 #include <net/ip6_tunnel.h>
@@ -561,7 +562,7 @@ int __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
        struct ipv6_pinfo *np;
        const struct ipv6hdr *hdr = (const struct ipv6hdr *)skb->data;
        const struct in6_addr *saddr = &hdr->saddr;
-       const struct in6_addr *daddr = &hdr->daddr;
+       const struct in6_addr *daddr = seg6_get_daddr(skb, opt) ? : &hdr->daddr;
        struct udphdr *uh = (struct udphdr *)(skb->data+offset);
        bool tunnel = false;
        struct sock *sk;