Re: [Qemu-devel] [PATCH 1/1] Migration: libvirt live migration over RDMA of ipv6 addr failed

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* David Dai (zdai@linux.vnet.ibm.com) 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").


Hi David,
  I'm ccing in some libvirt guys here; this might be a bug that
libvirt should be leaving the []'s on when it calls qemu.

Lets just check with Jiri and Dan (who I've added to the mail) to see what
they thing libvirt should be doing here.

Dave

> 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).
> 
> Signed-off-by: David Dai <zdai@linux.vnet.ibm.com>
> ---
>  util/qemu-sockets.c |   28 +++++++++++++++++++++++-----
>  1 files changed, 23 insertions(+), 5 deletions(-)
> 
> diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
> index 7c120c4..e09191c 100644
> --- a/util/qemu-sockets.c
> +++ b/util/qemu-sockets.c
> @@ -584,6 +584,8 @@ InetSocketAddress *inet_parse(const char *str, Error **errp)
>      char port[33];
>      int to;
>      int pos;
> +    char *first_col_p = strchr(str, ':');
> +    char *last_col_p = strrchr(str, ':');
>  
>      addr = g_new0(InetSocketAddress, 1);
>  
> @@ -595,11 +597,27 @@ InetSocketAddress *inet_parse(const char *str, Error **errp)
>              error_setg(errp, "error parsing port in address '%s'", str);
>              goto fail;
>          }
> -    } else if (str[0] == '[') {
> -        /* IPv6 addr */
> -        if (sscanf(str, "[%64[^]]]:%32[^,]%n", host, port, &pos) != 2) {
> -            error_setg(errp, "error parsing IPv6 address '%s'", str);
> -            goto fail;
> +    } else if (first_col_p != last_col_p) {
> +        if (str[0] != '[') {
> +            /* IPv6 addr w/o brackets */
> +            char *port_p;
> +            char *comma_p;
> +
> +            pstrcpy(host, sizeof(host), str);
> +            port_p = strrchr(host, ':');
> +            *port_p++ = '\0';
> +            pstrcpy(port, sizeof(port), port_p);
> +            comma_p = strchr(port, ',');
> +            if (comma_p != NULL) {
> +                *comma_p = '\0';
> +            }
> +            pos = strlen(host) + strlen(port) + 1;
> +        } else {
> +            /* IPv6 addr with brackets */
> +            if (2 != sscanf(str, "[%64[^]]]:%32[^,]%n", host, port, &pos)) {
> +                error_setg(errp, "error parsing IPv6 address '%s'", str);
> +                goto fail;
> +            }
>          }
>          addr->ipv6 = addr->has_ipv6 = true;
>      } else {
> -- 
> 1.7.1
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK