Re: Should we allow to configure twice the same IP?
On Tue, Oct 28, 2014 at 11:55:57AM +0100, Martin Pieuchot wrote: There's nothing that prevent you to configure the same IPv4 address on different interfaces in the same routing domain. But does it make sense? Yes, it does make sense. I abuse this feature to get unnumbered point-to-point links. Index: netinet/in.c === RCS file: /home/ncvs/src/sys/netinet/in.c,v retrieving revision 1.106 diff -u -p -r1.106 in.c --- netinet/in.c 7 Oct 2014 08:47:28 - 1.106 +++ netinet/in.c 28 Oct 2014 10:23:07 - @@ -616,6 +616,10 @@ in_ifinit(struct ifnet *ifp, struct in_i splsoftassert(IPL_SOFTNET); + /* Make sure this address does not exist in the given rdomain. */ + if (ifa_ifwithaddr(sintosa(sin), ifp-if_rdomain)) + return (EEXIST); + if (newaddr) TAILQ_INSERT_TAIL(in_ifaddr, ia, ia_list); -- :wq Claudio
Re: Should we allow to configure twice the same IP?
On 14-10-28 05:55 AM, Martin Pieuchot wrote: There's nothing that prevent you to configure the same IPv4 address on different interfaces in the same routing domain. But does it make sense? Index: netinet/in.c === RCS file: /home/ncvs/src/sys/netinet/in.c,v retrieving revision 1.106 diff -u -p -r1.106 in.c --- netinet/in.c7 Oct 2014 08:47:28 - 1.106 +++ netinet/in.c28 Oct 2014 10:23:07 - @@ -616,6 +616,10 @@ in_ifinit(struct ifnet *ifp, struct in_i splsoftassert(IPL_SOFTNET); + /* Make sure this address does not exist in the given rdomain. */ + if (ifa_ifwithaddr(sintosa(sin), ifp-if_rdomain)) + return (EEXIST); + if (newaddr) TAILQ_INSERT_TAIL(in_ifaddr, ia, ia_list); It might be needful when reconfiguring networks; if I swap two interfaces' IP addresses in /etc/hostname.* and re-run /etc/netstart instead of rebooting, I suspect this might break - I believe there would be a very brief overlap where two interfaces had the same IP address. Come to think of it, I'm not even sure whether this even works or not as-is; any opinions on what would be the canonical approach to swapping IPs between interfaces on a live system? Just do it by hand? Write your own script? Use netstart? Or just reboot? -- -Adam Thompson athom...@athompso.net
Re: Should we allow to configure twice the same IP?
On 28/10/14(Tue) 08:57, Adam Thompson wrote: On 14-10-28 05:55 AM, Martin Pieuchot wrote: There's nothing that prevent you to configure the same IPv4 address on different interfaces in the same routing domain. But does it make sense? Index: netinet/in.c === RCS file: /home/ncvs/src/sys/netinet/in.c,v retrieving revision 1.106 diff -u -p -r1.106 in.c --- netinet/in.c 7 Oct 2014 08:47:28 - 1.106 +++ netinet/in.c 28 Oct 2014 10:23:07 - @@ -616,6 +616,10 @@ in_ifinit(struct ifnet *ifp, struct in_i splsoftassert(IPL_SOFTNET); +/* Make sure this address does not exist in the given rdomain. */ +if (ifa_ifwithaddr(sintosa(sin), ifp-if_rdomain)) +return (EEXIST); + if (newaddr) TAILQ_INSERT_TAIL(in_ifaddr, ia, ia_list); It might be needful when reconfiguring networks; if I swap two interfaces' IP addresses in /etc/hostname.* and re-run /etc/netstart instead of rebooting, I suspect this might break - I believe there would be a very brief overlap where two interfaces had the same IP address. The scenario you're describing is already broken :) Did you try? Come to think of it, I'm not even sure whether this even works or not as-is; any opinions on what would be the canonical approach to swapping IPs between interfaces on a live system? Just do it by hand? Write your own script? Use netstart? Or just reboot? Nobody published a tool that would do that properly, so for the moment do it by hand or reboot your machine.
