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Date: Fri, 25 Jun 2021 17:27:37 +0200
From: Pali Rohár <pali@...nel.org>
To: Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc: Marek Behún <kabel@...nel.org>,
netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
linux-kernel@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
Russell King <rmk+kernel@...linux.org.uk>,
Stephen Hemminger <stephen@...workplumber.org>,
Phil Sutter <phil@....cc>
Subject: Re: Issues during assigning addresses on point to point interfaces
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@...nel.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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