On Tue, Jan 24, 2017 at 09:44:33AM -0600, David Dai wrote:
> Using libvirt to do live migration over RDMA via ip v6 address failed.
> For example:
> # virsh migrate --live --migrateuri rdma://[deba::2222]:49152 \
> rhel73_host1_guest1 qemu+ssh://[deba::2222]/system --verbose
> root@deba::2222's password:
> error: internal error: unable to execute QEMU command 'migrate': RDMA ERROR:
> could not rdma_getaddrinfo address deba
>
> As we can see, the ip v6 address used by rdma_getaddrinfo() has only "deba"
> part. It should be "deba::2222".
>
> 1) According to rfc 3986, a literal ip v6 address should be enclosed
> in '[' and ']'.
> When using virsh command to do live migration via ip v6 addresss, user
> will input the ip v6 address with brackets (i.e. rdma://[deba::2222]:49152).
> libvirt will parse command line option by calling virURIParse().
> Inside it calls virStringStripIPv6Brackets() to strip off the brackets.
> The uri passed in to virURIParse() is:
> "uri = rdma://[deba::2222]:49152"
> Inside virURIParse() routine, it will strip off the bracket '[' and ']' if
> it's ip v6 address. Then save the ip v6 address in this format "deba::2222"
> in the virURI->server field, and to be passed to qemu.
>
> 2) At the beginning of migration, in qemu's qemu_rdma_data_init(host_port)
> routine, it calls inet_parse(host_port) routine to parse the ip v6 address
> and
> port string obtained from libvirt.
> The input string host_port passed to qemu_rdma_data_init() can be:
> "hostname:port", or
> "ipv4address:port", or
> "[ipv6address]:port" (i.e "[deba::2222]:49152"), or
> "ipv6address:port" (i.e "deba::2222:49152").
> Existing qemu api inet_parse() can handle the above first 3 cases properly,
> but didn't handle the last case ("ipv6address:port") correctly.
> In this live migration over rdma via ip v6 address case, the server ip v6
> address obtained from libvirt doesn't contain the brackets '[' and ']'
> (i.e. "deba::2222:49152"). It caused inet_parse() to parse only "deba" part,
> and stopped at the 1st colon ':'. As the result, the subsequent
> rdma_getaddrinfo() with ip address "deba" will fail.
>
> If we don't strip off brackets '[' and ']' for an ip v6 address in libvirt's
> virURIParse(), it will cause libvirt ipv6 ssh authentication failure.
>
> NOTE:
> If using libvirt to do live migration over TCP via ip v6 address:
> # virsh migrate --live --migrateuri tcp://[deba::2222]:49152 \
> rhel73_host1_guest1 qemu+ssh://[deba::2222]/system --verbose
> It works fine.
> In migrateuri of tcp case, libvirt will call virNetSocketNewConnectTCP()
> directly to connect to remote "deba::2222:49152" after it strips off
> the bracket '[' and ']' for an ip v6 address.
> On qemu side, fd_start_outgoing_migration() will be called to do migration.
> It doesn't call inet_parse(). So we don't see issue in tcp case.
>
> Solution:
> I choose to fix the code in qemu's inet_parse() routine to parse the
> ip v6 addresss w/o brackets properly (i.e. "deba::2222:49152" format).
That is not right - "deba::222:49152" is *not* a valid address. It
is mandatory to use [] when providing a numeric IPv6 address. So
there's nothing broken in QEMU here - libvirt needs fixing to pass
correct data to QEMU
Regards,
Daniel
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