Messages in this thread | | | Date | Fri, 25 Jun 2021 17:27:37 +0200 | From | Pali Rohár <> | Subject | Re: Issues during assigning addresses on point to point interfaces |
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On Friday 25 June 2021 17:06:21 Nicolas Dichtel wrote: > Le 25/06/2021 à 10:40, Pali Rohár a écrit : > > On Thursday 24 June 2021 14:57:41 Nicolas Dichtel wrote: > >> Le 24/06/2021 à 12:45, Marek Behún a écrit : > >>> On Sun, 6 Jun 2021 17:10:08 +0200 > >>> Pali Rohár <pali@kernel.org> wrote: > >>> > >>>> Hello! > >>>> > >>>> Seems that there is a bug during assigning IP addresses on point to > >>>> point interfaces. > >>>> > >>>> Assigning just one local address works fine: > >>>> > >>>> ip address add fe80::6 dev ppp1 --> inet6 fe80::6/128 scope link > >>>> > >>>> Assigning both local and remote peer address also works fine: > >>>> > >>>> ip address add fe80::7 peer fe80::8 dev ppp1 ---> inet6 fe80::7 > >>>> peer fe80::8/128 scope link > >>>> > >>>> But trying to assign just remote peer address does not work. Moreover > >>>> "ip address" call does not fail, it returns zero but instead of > >>>> setting remote peer address, it sets local address: > >>>> > >>>> ip address add peer fe80::5 dev ppp1 --> inet6 fe80::5/128 scope > >>>> link > >>>> > >>> > >>> Adding some other people to Cc in order to get their opinions. > >>> > >>> It seems this bug is there from the beginning, from commit > >>> caeaba79009c2 ("ipv6: add support of peer address") > >>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=caeaba79009c2 > >>> > >>> Maybe some older user-space utilities use IFA_ADDRESS instead of > >>> IFA_LOCAL, and this was done in order to be compatible with them? > >> If I remember well, there was an issue in the uAPI. > >> IFA_LOCAL is supposed to be the address of the interface and IFA_ADDRESS is > >> supposed to be the endpoint of a point-to-point interface. > >> However, in case of IPv6, it was not the case. In netlink messages generated by > >> the kernel, IFA_ADDRESS was used instead of IFA_LOCAL. > >> The patch tried to keep the backward compatibility and the symmetry between msg > >> from userland and notification from the kernel. > > > > Hello Nicolas! > > > > See my original email where I put also rtnetlink packets (how strace see > > them). Seems that there is a bug in handling them (or bug in iproute2) > > as setting just peer (remote) IPv6 address is ignored: > > https://lore.kernel.org/netdev/20210606151008.7dwx5ukrlvxt4t3k@pali/ > > > > Do you have any idea if this is affected by that "issue in the uAPI"? > > And what is the way how to fix it? > What about forcing IFA_LOCAL address to :: in your case?
It does not work. ip address returns error:
$ sudo ip address add :: peer fe80::8 dev ppp0 RTNETLINK answers: Cannot assign requested address
Here is strace output:
sendmsg(3, { msg_name={ sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000 }, msg_namelen=12, msg_iov=[{ iov_base={ { len=64, type=RTM_NEWADDR, flags=NLM_F_REQUEST|NLM_F_ACK|NLM_F_EXCL|NLM_F_CREATE, seq=1624633811, pid=0 }, { ifa_family=AF_INET6, ifa_prefixlen=128, ifa_flags=0, ifa_scope=RT_SCOPE_UNIVERSE, ifa_index=if_nametoindex("ppp0") }, [ { { nla_len=20, nla_type=IFA_LOCAL }, inet_pton(AF_INET6, "::") }, { { nla_len=20, nla_type=IFA_ADDRESS }, inet_pton(AF_INET6, "fe80::8") } ] }, iov_len=64 }], msg_iovlen=1, msg_controllen=0, msg_flags=0 }, 0) = 64
recvmsg(3, { msg_name={ sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000 }, msg_namelen=12, msg_iov=[{ iov_base=NULL, iov_len=0 }], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_TRUNC }, MSG_PEEK|MSG_TRUNC) = 84
recvmsg(3, { msg_name={ sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000 }, msg_namelen=12, msg_iov=[{ iov_base={ { len=84, type=NLMSG_ERROR, flags=0, seq=1624633811, pid=3698 }, { error=-EADDRNOTAVAIL, msg={ { len=64, type=RTM_NEWADDR, flags=NLM_F_REQUEST|NLM_F_ACK|NLM_F_EXCL|NLM_F_CREATE, seq=1624633811, pid=0 }, { ifa_family=AF_INET6, ifa_prefixlen=128, ifa_flags=0, ifa_scope=RT_SCOPE_UNIVERSE, ifa_index=if_nametoindex("ppp0") }, [ { { nla_len=20, nla_type=IFA_LOCAL }, inet_pton(AF_INET6, "::") }, { { nla_len=20, nla_type=IFA_ADDRESS }, inet_pton(AF_INET6, "fe80::8") } ] } } }, iov_len=84 }], msg_iovlen=1, msg_controllen=0, msg_flags=0 }, 0) = 84
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