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authorFrancesco Ruggeri <fruggeri@arista.com>2019-10-30 17:40:02 -0700
committerDavid S. Miller <davem@davemloft.net>2019-11-03 17:26:53 -0800
commitfac6fce9bdb59837bb89930c3a92f5e0d1482f0b (patch)
tree9b18dd3e8d658e69402bb9384b66eef88b401ebb /net/ipv6/icmp.c
parent06e7c70c6e8903da57982ab3bdc81e01a8ba941d (diff)
net: icmp6: provide input address for traceroute6
traceroute6 output can be confusing, in that it shows the address that a router would use to reach the sender, rather than the address the packet used to reach the router. Consider this case: ------------------------ N2 | | ------ ------ N3 ---- | R1 | | R2 |------|H2| ------ ------ ---- | | ------------------------ N1 | ---- |H1| ---- where H1's default route is through R1, and R1's default route is through R2 over N2. traceroute6 from H1 to H2 shows R2's address on N1 rather than on N2. The script below can be used to reproduce this scenario. traceroute6 output without this patch: traceroute to 2000:103::4 (2000:103::4), 30 hops max, 80 byte packets 1 2000:101::1 (2000:101::1) 0.036 ms 0.008 ms 0.006 ms 2 2000:101::2 (2000:101::2) 0.011 ms 0.008 ms 0.007 ms 3 2000:103::4 (2000:103::4) 0.013 ms 0.010 ms 0.009 ms traceroute6 output with this patch: traceroute to 2000:103::4 (2000:103::4), 30 hops max, 80 byte packets 1 2000:101::1 (2000:101::1) 0.056 ms 0.019 ms 0.006 ms 2 2000:102::2 (2000:102::2) 0.013 ms 0.008 ms 0.008 ms 3 2000:103::4 (2000:103::4) 0.013 ms 0.009 ms 0.009 ms #!/bin/bash # # ------------------------ N2 # | | # ------ ------ N3 ---- # | R1 | | R2 |------|H2| # ------ ------ ---- # | | # ------------------------ N1 # | # ---- # |H1| # ---- # # N1: 2000:101::/64 # N2: 2000:102::/64 # N3: 2000:103::/64 # # R1's host part of address: 1 # R2's host part of address: 2 # H1's host part of address: 3 # H2's host part of address: 4 # # For example: # the IPv6 address of R1's interface on N2 is 2000:102::1/64 # # Nets are implemented by macvlan interfaces (bridge mode) over # dummy interfaces. # # Create net namespaces ip netns add host1 ip netns add host2 ip netns add rtr1 ip netns add rtr2 # Create nets ip link add net1 type dummy; ip link set net1 up ip link add net2 type dummy; ip link set net2 up ip link add net3 type dummy; ip link set net3 up # Add interfaces to net1, move them to their nemaspaces ip link add link net1 dev host1net1 type macvlan mode bridge ip link set host1net1 netns host1 ip link add link net1 dev rtr1net1 type macvlan mode bridge ip link set rtr1net1 netns rtr1 ip link add link net1 dev rtr2net1 type macvlan mode bridge ip link set rtr2net1 netns rtr2 # Add interfaces to net2, move them to their nemaspaces ip link add link net2 dev rtr1net2 type macvlan mode bridge ip link set rtr1net2 netns rtr1 ip link add link net2 dev rtr2net2 type macvlan mode bridge ip link set rtr2net2 netns rtr2 # Add interfaces to net3, move them to their nemaspaces ip link add link net3 dev rtr2net3 type macvlan mode bridge ip link set rtr2net3 netns rtr2 ip link add link net3 dev host2net3 type macvlan mode bridge ip link set host2net3 netns host2 # Configure interfaces and routes in host1 ip netns exec host1 ip link set lo up ip netns exec host1 ip link set host1net1 up ip netns exec host1 ip -6 addr add 2000:101::3/64 dev host1net1 ip netns exec host1 ip -6 route add default via 2000:101::1 # Configure interfaces and routes in rtr1 ip netns exec rtr1 ip link set lo up ip netns exec rtr1 ip link set rtr1net1 up ip netns exec rtr1 ip -6 addr add 2000:101::1/64 dev rtr1net1 ip netns exec rtr1 ip link set rtr1net2 up ip netns exec rtr1 ip -6 addr add 2000:102::1/64 dev rtr1net2 ip netns exec rtr1 ip -6 route add default via 2000:102::2 ip netns exec rtr1 sysctl net.ipv6.conf.all.forwarding=1 # Configure interfaces and routes in rtr2 ip netns exec rtr2 ip link set lo up ip netns exec rtr2 ip link set rtr2net1 up ip netns exec rtr2 ip -6 addr add 2000:101::2/64 dev rtr2net1 ip netns exec rtr2 ip link set rtr2net2 up ip netns exec rtr2 ip -6 addr add 2000:102::2/64 dev rtr2net2 ip netns exec rtr2 ip link set rtr2net3 up ip netns exec rtr2 ip -6 addr add 2000:103::2/64 dev rtr2net3 ip netns exec rtr2 sysctl net.ipv6.conf.all.forwarding=1 # Configure interfaces and routes in host2 ip netns exec host2 ip link set lo up ip netns exec host2 ip link set host2net3 up ip netns exec host2 ip -6 addr add 2000:103::4/64 dev host2net3 ip netns exec host2 ip -6 route add default via 2000:103::2 # Ping host2 from host1 ip netns exec host1 ping6 -c5 2000:103::4 # Traceroute host2 from host1 ip netns exec host1 traceroute6 2000:103::4 # Delete nets ip link del net3 ip link del net2 ip link del net1 # Delete namespaces ip netns del rtr2 ip netns del rtr1 ip netns del host2 ip netns del host1 Signed-off-by: Francesco Ruggeri <fruggeri@arista.com> Original-patch-by: Honggang Xu <hxu@arista.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6/icmp.c')
-rw-r--r--net/ipv6/icmp.c22
1 files changed, 17 insertions, 5 deletions
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 62c997201970..ef408a5090a2 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -516,13 +516,29 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
mip6_addr_swap(skb);
+ sk = icmpv6_xmit_lock(net);
+ if (!sk)
+ goto out_bh_enable;
+
memset(&fl6, 0, sizeof(fl6));
fl6.flowi6_proto = IPPROTO_ICMPV6;
fl6.daddr = hdr->saddr;
if (force_saddr)
saddr = force_saddr;
- if (saddr)
+ if (saddr) {
fl6.saddr = *saddr;
+ } else {
+ /* select a more meaningful saddr from input if */
+ struct net_device *in_netdev;
+
+ in_netdev = dev_get_by_index(net, IP6CB(skb)->iif);
+ if (in_netdev) {
+ ipv6_dev_get_saddr(net, in_netdev, &fl6.daddr,
+ inet6_sk(sk)->srcprefs,
+ &fl6.saddr);
+ dev_put(in_netdev);
+ }
+ }
fl6.flowi6_mark = mark;
fl6.flowi6_oif = iif;
fl6.fl6_icmp_type = type;
@@ -531,10 +547,6 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
fl6.mp_hash = rt6_multipath_hash(net, &fl6, skb, NULL);
security_skb_classify_flow(skb, flowi6_to_flowi(&fl6));
- sk = icmpv6_xmit_lock(net);
- if (!sk)
- goto out_bh_enable;
-
sk->sk_mark = mark;
np = inet6_sk(sk);