Bug#941026: netcfg_gateway_reachable wrongly rejects IPv6 link-local addresses
On Wed, Oct 02, 2019 at 08:27:34AM +0200, Philipp Kern wrote: > On 2019-09-23 18:00, Andrew Kanaber wrote: > > When doing static IP configuration, netcfg will reject a gateway address > > outside the host's network as defined by the netmask. > So how does it identify the interface to use in this case? Does the kernel > have special support to pick the correct one if there is only one > non-loopback interface? Generally link-local addresses do need to be > qualified with the interface to be used. The routing table entry contains both the gateway address and the interface to use. When the kernel decides to use the route it has everything it needs. Using a link-local gateway is an entirely standard thing to do. It would have been reasonable for netcfg to reject link-local addresses entered as the actual host address - but it doesn't check for that, it just does this netmask check that happens to reject global unicast host address plus link-local gateway. Thanks, Andrew
Bug#941026: netcfg_gateway_reachable wrongly rejects IPv6 link-local addresses
On 2019-09-23 18:00, Andrew Kanaber wrote: When doing static IP configuration, netcfg will reject a gateway address outside the host's network as defined by the netmask. This is wrong for IPv6 because the gateway can legitimately be a link-local address in fe80::/64 instead of the host's network range. Ubuntu have fixed this bug in their version, see LP#1382295 https://bugs.launchpad.net/ubuntu/+source/netcfg/+bug/1382295 The relevant function is netcfg_gateway_reachable in netcfg-common.c which simply checks gateway_address & netmask == host_address. It should also allow IPv6 addresses in the link local prefix fe80::/64. Less importantly, the error message it triggers could be a bit clearer, "The gateway address you entered is unreachable" sounds like it might be a network error when it's purely a user-input parsing rejection - if the code had actually tried the link-local address it would've worked. So how does it identify the interface to use in this case? Does the kernel have special support to pick the correct one if there is only one non-loopback interface? Generally link-local addresses do need to be qualified with the interface to be used. Kind regards Philipp Kern
Bug#941026: netcfg_gateway_reachable wrongly rejects IPv6 link-local addresses
Package: netcfg Version: 1.160 Severity: normal When doing static IP configuration, netcfg will reject a gateway address outside the host's network as defined by the netmask. This is wrong for IPv6 because the gateway can legitimately be a link-local address in fe80::/64 instead of the host's network range. Ubuntu have fixed this bug in their version, see LP#1382295 https://bugs.launchpad.net/ubuntu/+source/netcfg/+bug/1382295 The relevant function is netcfg_gateway_reachable in netcfg-common.c which simply checks gateway_address & netmask == host_address. It should also allow IPv6 addresses in the link local prefix fe80::/64. Less importantly, the error message it triggers could be a bit clearer, "The gateway address you entered is unreachable" sounds like it might be a network error when it's purely a user-input parsing rejection - if the code had actually tried the link-local address it would've worked. Thanks for your help, Andrew Kanaber
