On Tue, 2015-11-24 at 12:44 +0100, Phil Sutter wrote: > On Mon, Nov 23, 2015 at 04:04:50PM -0800, Stephen Hemminger wrote: > > On Thu, 22 Oct 2015 10:34:28 +0200 > > Thomas Haller <thal...@redhat.com> wrote: > > > > > Kernel allows for zero IPv4 peer addresses (IFA_ADDRESS): > > > > > > ip address add 192.168.5.1 peer 0.0.0.0/24 dev dummy > > > > > > which is distinct from a usual address like: > > > > > > ip address add 192.168.5.1/24 dev dummy > > > ip address add 192.168.5.1 peer 192.168.5.1/24 dev dummy > > > > > > For IPv4, a missing IFA_ADDRESS attribute means that the peer > > > is 0.0.0.0. See inet_fill_ifaddr(), which does: > > > > > > if ((ifa->ifa_address && > > > nla_put_in_addr(skb, IFA_ADDRESS, ifa->ifa_address)) || > > > > > > Signed-off-by: Thomas Haller <thal...@redhat.com> > > > > I would prefer that this apply to both IPv4 and IPv6. > > The case that patch handles does not happen in IPv6. > > > If the kernel sends back an address, then display it. > > It's rather "if the kernel *does not* send back an address ...". > > When reviewing this patch, I tried to find an easier (and less ugly) > solution, but failed. Here's the result from testing all variants:
Thank you Phil for evaluating this. I also tried to change the patch to come up with a cleaner/unified way, but the result wasn't subjectively better. Thomas For reference, the relevant lines of code from kernel: ipv4: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/net/ipv4/devinet.c?id=6a13feb9c82803e2b815eca72fa7a9f5561d7861#n1542 if ((ifa->ifa_address && nla_put_in_addr(skb, IFA_ADDRESS, ifa->ifa_address)) || (ifa->ifa_local && nla_put_in_addr(skb, IFA_LOCAL, ifa->ifa_local)) || ipv6: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/net/ipv6/addrconf.c?id=6a13feb9c82803e2b815eca72fa7a9f5561d7861#n4310 if (!ipv6_addr_any(&ifa->peer_addr)) { if (nla_put_in6_addr(skb, IFA_LOCAL, &ifa->addr) < 0 || nla_put_in6_addr(skb, IFA_ADDRESS, &ifa->peer_addr) < 0) goto error; } else if (nla_put_in6_addr(skb, IFA_ADDRESS, &ifa->addr) < 0) goto error;
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