[PATCH] net: fix multicast support with BSD (macOS) socket implementations

[PATCH] net: fix multicast support with BSD (macOS) socket implementations

[Vitaly Cheptsov]

This patch fixes socket communication with QEMU -> host on macOS,
which was originally impossible due to QEMU and host program
having to bind to the same ip/port in a way not supported by BSD
sockets. The change was tested on both Linux and macOS.

As per BSD manual pages SO_REUSEPORT allows completely duplicate
bindings by multiple processes, permitting multiple instances of
a program to each receive UDP/IP multicast datagrams destined
for the bound port. Without this option macOS, unlike Linux,
which (ab)uses SO_REUSEADDR for this purpose, will return
"Address already in use" on bind().

As per BSD manual pages binding to any address, even one not bound
to any available network interface in the system, should be
IP_BINDANY. Without binding to INADDR_ANY macOS will return
"Can't assign requested address" on send().

Cc: Jason Wang <jasowang@redhat.com>
Cc: Daniel P. Berrange <berrange@redhat.com>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Vitaly Cheptsov <cheptsov@ispras.ru>
---
 net/socket.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/net/socket.c b/net/socket.c
index ea5220a2eb..8b2c6c4bb8 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -252,10 +252,24 @@ static int net_socket_mcast_create(struct sockaddr_in *mcastaddr,
         goto fail;
     }
 
-    ret = bind(fd, (struct sockaddr *)mcastaddr, sizeof(*mcastaddr));
+    val = 1;
+    ret = qemu_setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &val, sizeof(val));
+    if (ret < 0) {
+        error_setg_errno(errp, errno,
+                         "can't set socket option SO_REUSEPORT");
+        goto fail;
+    }
+
+    struct sockaddr_in bindaddr;
+    memset(&bindaddr, 0, sizeof(bindaddr));
+    bindaddr.sin_family = AF_INET;
+    bindaddr.sin_addr.s_addr = htonl(INADDR_ANY);
+    bindaddr.sin_port = mcastaddr->sin_port;
+    ret = bind(fd, (struct sockaddr *)&bindaddr, sizeof(bindaddr));
+
     if (ret < 0) {
         error_setg_errno(errp, errno, "can't bind ip=%s to socket",
-                         inet_ntoa(mcastaddr->sin_addr));
+                         inet_ntoa(bindaddr.sin_addr));
         goto fail;
     }
 
-- 
2.32.0 (Apple Git-132)

Re: [PATCH] net: fix multicast support with BSD (macOS) socket implementations

[Daniel P. Berrangé]

On Mon, May 02, 2022 at 03:38:30AM +0300, Vitaly Cheptsov wrote:
> This patch fixes socket communication with QEMU -> host on macOS,
> which was originally impossible due to QEMU and host program
> having to bind to the same ip/port in a way not supported by BSD
> sockets. The change was tested on both Linux and macOS.
> 
> As per BSD manual pages SO_REUSEPORT allows completely duplicate
> bindings by multiple processes, permitting multiple instances of
> a program to each receive UDP/IP multicast datagrams destined
> for the bound port. Without this option macOS, unlike Linux,
> which (ab)uses SO_REUSEADDR for this purpose, will return
> "Address already in use" on bind().


When looking in Google there's a comprehensive looking
description of SO_REUSEADDR + SO_REUSEPORT across all the
different OS which insists that SO_REUSEPORT and SO_REUSEADDR
are functionally equivalent for multicast IP addresses:

  https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ

And AFAIK, macOS should behave the same way, which suggests
this patch is not needed.

Oddly though, I don't find this in the FreeBSD man page - its
description seems fairly clear that SO_REUSEPORT is needed for
multicast

[quote]
     SO_REUSEPORT allows completely duplicate bindings by multiple processes
     if they all set SO_REUSEPORT before binding the port.  This option
     permits multiple instances of a program to each receive UDP/IP multicast
     or broadcast datagrams destined for the bound port.
[/quote]


> 
> As per BSD manual pages binding to any address, even one not bound
> to any available network interface in the system, should be
> IP_BINDANY. Without binding to INADDR_ANY macOS will return
> "Can't assign requested address" on send().

I didn't find a quote about this in the FreeBSD man pages I looked
at, and it feels dubious to me. If the user gives QEMU a address to
bind to, we should surely be honouring that, not changing it to
INADDR_ANY.

If using INADDR_ANY though, thsi could explain the need for
SO_REUSEPORT, since INADDR_ANY is not a designated mcast address.

> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Daniel P. Berrange <berrange@redhat.com>
> Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
> Signed-off-by: Vitaly Cheptsov <cheptsov@ispras.ru>
> ---
>  net/socket.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/net/socket.c b/net/socket.c
> index ea5220a2eb..8b2c6c4bb8 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -252,10 +252,24 @@ static int net_socket_mcast_create(struct sockaddr_in *mcastaddr,
>          goto fail;
>      }
>  
> -    ret = bind(fd, (struct sockaddr *)mcastaddr, sizeof(*mcastaddr));
> +    val = 1;
> +    ret = qemu_setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &val, sizeof(val));
> +    if (ret < 0) {
> +        error_setg_errno(errp, errno,
> +                         "can't set socket option SO_REUSEPORT");
> +        goto fail;
> +    }

AFAIK, this likely won't compile on Windows since it lacks SO_REUSEPORT

> +
> +    struct sockaddr_in bindaddr;
> +    memset(&bindaddr, 0, sizeof(bindaddr));
> +    bindaddr.sin_family = AF_INET;
> +    bindaddr.sin_addr.s_addr = htonl(INADDR_ANY);
> +    bindaddr.sin_port = mcastaddr->sin_port;
> +    ret = bind(fd, (struct sockaddr *)&bindaddr, sizeof(bindaddr));
> +
>      if (ret < 0) {
>          error_setg_errno(errp, errno, "can't bind ip=%s to socket",
> -                         inet_ntoa(mcastaddr->sin_addr));
> +                         inet_ntoa(bindaddr.sin_addr));
>          goto fail;
>      }


With regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|

Re: [PATCH] net: fix multicast support with BSD (macOS) socket implementations

[Vitaly Cheptsov]

[-- Attachment #1: Type: text/plain, Size: 8326 bytes --]

Hi Daniel,

Thank you for your comment. Socket implementation on all the systems is rather complicated, and while I am fine to update the patch with better reasoning, it needs to work on macOS. Given the situation with Windows, I think we may want to ifdef the change to be macOS-specific.

Other than that, perhaps, we can come to something better if you give some ideas what should we try. So far this was the only working combination, however. If you do not have the hardware, I am can perform these tests for you.

To simplify the situation, I attached two minimal python scripts, which closely resemble QEMU actions, and allow testing bidirectional multicast sockets.

> When looking in Google there's a comprehensive looking
> description of SO_REUSEADDR + SO_REUSEPORT across all the
> different OS which insists that SO_REUSEPORT and SO_REUSEADDR
> are functionally equivalent for multicast IP addresses:
> 
> https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ
> 
> And AFAIK, macOS should behave the same way, which suggests
> this patch is not needed.
> 
> Oddly though, I don't find this in the FreeBSD man page - its
> description seems fairly clear that SO_REUSEPORT is needed for
> multicast
> 
> [quote]
> SO_REUSEPORT allows completely duplicate bindings by multiple processes
> if they all set SO_REUSEPORT before binding the port. This option
> permits multiple instances of a program to each receive UDP/IP multicast
> or broadcast datagrams destined for the bound port.
> [/quote]

I also saw this description, and it is possible it is a little outdated. I can safely (entirely) drop setting SO_REUSEADDR on macOS, but it will not work without socket.SO_REUSEPORT. This can be easily proven with a.py/b.py.

> I didn't find a quote about this in the FreeBSD man pages I looked
> at, and it feels dubious to me. If the user gives QEMU a address to
> bind to, we should surely be honouring that, not changing it to
> INADDR_ANY.
> 
> If using INADDR_ANY though, thsi could explain the need for
> SO_REUSEPORT, since INADDR_ANY is not a designated mcast address.

I made this judgement from the following part of ip(4):

> If the IP_BINDANY option is enabled on a SOCK_STREAM, SOCK_DGRAM or a
> SOCK_RAW socket, one can bind(2) to any address, even one not bound to
> any available network interface in the system.


This makes some sense, because if I change a.py and b.py
- to bind to MCAST_GRP instead of “0.0.0.0”
- to not set SO_REUSEPORT

I get "Can't assign requested address” error at sendto in b.py. Same thing happens in QEMU.

Best regards,
Vitaly


# a.py
import socket
import struct
import scapy.all as scapy

MCAST_GRP = '230.0.0.1'
MCAST_PORT = 1234
MULTICAST_TTL = 2
MAX_PACKET_SIZE = 65535

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
sock.bind(("0.0.0.0", MCAST_PORT))
mreq = struct.pack('4sL', socket.inet_aton(MCAST_GRP), socket.INADDR_ANY)
sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)

data, _ = sock.recvfrom(MAX_PACKET_SIZE)
print(data)
sock.sendto(b"message_from_a", (MCAST_GRP, MCAST_PORT))

# b.py
import socket
import struct
import scapy.all as scapy

MCAST_GRP = '230.0.0.1'
MCAST_PORT = 1234
MULTICAST_TTL = 2
MAX_PACKET_SIZE = 65535

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, 0)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
sock.bind(("0.0.0.0", MCAST_PORT))
mreq = struct.pack('4sL', socket.inet_aton(MCAST_GRP), socket.INADDR_ANY)
sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)

sock.sendto(b"message_from_b", (MCAST_GRP, MCAST_PORT))

data, _ = sock.recvfrom(MAX_PACKET_SIZE)
print(data)

data, _ = sock.recvfrom(MAX_PACKET_SIZE)
print(data)

% python3 ./a.py
WARNING: No IPv4 address found on en2 !
WARNING: No IPv4 address found on en1 !
WARNING: more No IPv4 address found on p2p0 !
b'message_from_b'

% python3 ./b.py
WARNING: No IPv4 address found on en2 !
WARNING: No IPv4 address found on en1 !
WARNING: more No IPv4 address found on p2p0 !
b'message_from_b'
b'message_from_a'

> On 3 May 2022, at 16:13, Daniel P. Berrangé <berrange@redhat.com> wrote:
> 
> On Mon, May 02, 2022 at 03:38:30AM +0300, Vitaly Cheptsov wrote:
>> This patch fixes socket communication with QEMU -> host on macOS,
>> which was originally impossible due to QEMU and host program
>> having to bind to the same ip/port in a way not supported by BSD
>> sockets. The change was tested on both Linux and macOS.
>> 
>> As per BSD manual pages SO_REUSEPORT allows completely duplicate
>> bindings by multiple processes, permitting multiple instances of
>> a program to each receive UDP/IP multicast datagrams destined
>> for the bound port. Without this option macOS, unlike Linux,
>> which (ab)uses SO_REUSEADDR for this purpose, will return
>> "Address already in use" on bind().
> 
> 
> When looking in Google there's a comprehensive looking
> description of SO_REUSEADDR + SO_REUSEPORT across all the
> different OS which insists that SO_REUSEPORT and SO_REUSEADDR
> are functionally equivalent for multicast IP addresses:
> 
> https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ
> 
> And AFAIK, macOS should behave the same way, which suggests
> this patch is not needed.
> 
> Oddly though, I don't find this in the FreeBSD man page - its
> description seems fairly clear that SO_REUSEPORT is needed for
> multicast
> 
> [quote]
> SO_REUSEPORT allows completely duplicate bindings by multiple processes
> if they all set SO_REUSEPORT before binding the port. This option
> permits multiple instances of a program to each receive UDP/IP multicast
> or broadcast datagrams destined for the bound port.
> [/quote]
> 
> 
>> 
>> As per BSD manual pages binding to any address, even one not bound
>> to any available network interface in the system, should be
>> IP_BINDANY. Without binding to INADDR_ANY macOS will return
>> "Can't assign requested address" on send().
> 
> I didn't find a quote about this in the FreeBSD man pages I looked
> at, and it feels dubious to me. If the user gives QEMU a address to
> bind to, we should surely be honouring that, not changing it to
> INADDR_ANY.
> 
> If using INADDR_ANY though, thsi could explain the need for
> SO_REUSEPORT, since INADDR_ANY is not a designated mcast address.
> 
>> Cc: Jason Wang <jasowang@redhat.com>
>> Cc: Daniel P. Berrange <berrange@redhat.com>
>> Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> Signed-off-by: Vitaly Cheptsov <cheptsov@ispras.ru>
>> ---
>> net/socket.c | 18 ++++++++++++++++--
>> 1 file changed, 16 insertions(+), 2 deletions(-)
>> 
>> diff --git a/net/socket.c b/net/socket.c
>> index ea5220a2eb..8b2c6c4bb8 100644
>> --- a/net/socket.c
>> +++ b/net/socket.c
>> @@ -252,10 +252,24 @@ static int net_socket_mcast_create(struct sockaddr_in *mcastaddr,
>> goto fail;
>> }
>> 
>> - ret = bind(fd, (struct sockaddr *)mcastaddr, sizeof(*mcastaddr));
>> + val = 1;
>> + ret = qemu_setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &val, sizeof(val));
>> + if (ret < 0) {
>> + error_setg_errno(errp, errno,
>> + "can't set socket option SO_REUSEPORT");
>> + goto fail;
>> + }
> 
> AFAIK, this likely won't compile on Windows since it lacks SO_REUSEPORT
> 
>> +
>> + struct sockaddr_in bindaddr;
>> + memset(&bindaddr, 0, sizeof(bindaddr));
>> + bindaddr.sin_family = AF_INET;
>> + bindaddr.sin_addr.s_addr = htonl(INADDR_ANY);
>> + bindaddr.sin_port = mcastaddr->sin_port;
>> + ret = bind(fd, (struct sockaddr *)&bindaddr, sizeof(bindaddr));
>> +
>> if (ret < 0) {
>> error_setg_errno(errp, errno, "can't bind ip=%s to socket",
>> - inet_ntoa(mcastaddr->sin_addr));
>> + inet_ntoa(bindaddr.sin_addr));
>> goto fail;
>> }
> 
> 
> With regards,
> Daniel
> --
> |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
> |: https://libvirt.org -o- https://fstop138.berrange.com :|
> |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|


[-- Attachment #2: Message signed with OpenPGP --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH] net: fix multicast support with BSD (macOS) socket implementations

[Vitaly Cheptsov]

[-- Attachment #1: Type: text/plain, Size: 8725 bytes --]

Gentle ping :)

> On 3 May 2022, at 19:10, Vitaly Cheptsov <cheptsov@ispras.ru> wrote:
> 
> Hi Daniel,
> 
> Thank you for your comment. Socket implementation on all the systems is rather complicated, and while I am fine to update the patch with better reasoning, it needs to work on macOS. Given the situation with Windows, I think we may want to ifdef the change to be macOS-specific.
> 
> Other than that, perhaps, we can come to something better if you give some ideas what should we try. So far this was the only working combination, however. If you do not have the hardware, I am can perform these tests for you.
> 
> To simplify the situation, I attached two minimal python scripts, which closely resemble QEMU actions, and allow testing bidirectional multicast sockets.
> 
>> When looking in Google there's a comprehensive looking
>> description of SO_REUSEADDR + SO_REUSEPORT across all the
>> different OS which insists that SO_REUSEPORT and SO_REUSEADDR
>> are functionally equivalent for multicast IP addresses:
>> 
>> https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ
>> 
>> And AFAIK, macOS should behave the same way, which suggests
>> this patch is not needed.
>> 
>> Oddly though, I don't find this in the FreeBSD man page - its
>> description seems fairly clear that SO_REUSEPORT is needed for
>> multicast
>> 
>> [quote]
>> SO_REUSEPORT allows completely duplicate bindings by multiple processes
>> if they all set SO_REUSEPORT before binding the port. This option
>> permits multiple instances of a program to each receive UDP/IP multicast
>> or broadcast datagrams destined for the bound port.
>> [/quote]
> 
> I also saw this description, and it is possible it is a little outdated. I can safely (entirely) drop setting SO_REUSEADDR on macOS, but it will not work without socket.SO_REUSEPORT. This can be easily proven with a.py/b.py.
> 
>> I didn't find a quote about this in the FreeBSD man pages I looked
>> at, and it feels dubious to me. If the user gives QEMU a address to
>> bind to, we should surely be honouring that, not changing it to
>> INADDR_ANY.
>> 
>> If using INADDR_ANY though, thsi could explain the need for
>> SO_REUSEPORT, since INADDR_ANY is not a designated mcast address.
> 
> I made this judgement from the following part of ip(4):
> 
>> If the IP_BINDANY option is enabled on a SOCK_STREAM, SOCK_DGRAM or a
>> SOCK_RAW socket, one can bind(2) to any address, even one not bound to
>> any available network interface in the system.
> 
> 
> This makes some sense, because if I change a.py and b.py
> - to bind to MCAST_GRP instead of “0.0.0.0”
> - to not set SO_REUSEPORT
> 
> I get "Can't assign requested address” error at sendto in b.py. Same thing happens in QEMU.
> 
> Best regards,
> Vitaly
> 
> 
> # a.py
> import socket
> import struct
> import scapy.all as scapy
> 
> MCAST_GRP = '230.0.0.1'
> MCAST_PORT = 1234
> MULTICAST_TTL = 2
> MAX_PACKET_SIZE = 65535
> 
> sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
> sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
> sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
> sock.bind(("0.0.0.0", MCAST_PORT))
> mreq = struct.pack('4sL', socket.inet_aton(MCAST_GRP), socket.INADDR_ANY)
> sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
> 
> data, _ = sock.recvfrom(MAX_PACKET_SIZE)
> print(data)
> sock.sendto(b"message_from_a", (MCAST_GRP, MCAST_PORT))
> 
> # b.py
> import socket
> import struct
> import scapy.all as scapy
> 
> MCAST_GRP = '230.0.0.1'
> MCAST_PORT = 1234
> MULTICAST_TTL = 2
> MAX_PACKET_SIZE = 65535
> 
> sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, 0)
> sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
> sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
> sock.bind(("0.0.0.0", MCAST_PORT))
> mreq = struct.pack('4sL', socket.inet_aton(MCAST_GRP), socket.INADDR_ANY)
> sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
> 
> sock.sendto(b"message_from_b", (MCAST_GRP, MCAST_PORT))
> 
> data, _ = sock.recvfrom(MAX_PACKET_SIZE)
> print(data)
> 
> data, _ = sock.recvfrom(MAX_PACKET_SIZE)
> print(data)
> 
> % python3 ./a.py
> WARNING: No IPv4 address found on en2 !
> WARNING: No IPv4 address found on en1 !
> WARNING: more No IPv4 address found on p2p0 !
> b'message_from_b'
> 
> % python3 ./b.py
> WARNING: No IPv4 address found on en2 !
> WARNING: No IPv4 address found on en1 !
> WARNING: more No IPv4 address found on p2p0 !
> b'message_from_b'
> b'message_from_a'
> 
>> On 3 May 2022, at 16:13, Daniel P. Berrangé <berrange@redhat.com> wrote:
>> 
>> On Mon, May 02, 2022 at 03:38:30AM +0300, Vitaly Cheptsov wrote:
>>> This patch fixes socket communication with QEMU -> host on macOS,
>>> which was originally impossible due to QEMU and host program
>>> having to bind to the same ip/port in a way not supported by BSD
>>> sockets. The change was tested on both Linux and macOS.
>>> 
>>> As per BSD manual pages SO_REUSEPORT allows completely duplicate
>>> bindings by multiple processes, permitting multiple instances of
>>> a program to each receive UDP/IP multicast datagrams destined
>>> for the bound port. Without this option macOS, unlike Linux,
>>> which (ab)uses SO_REUSEADDR for this purpose, will return
>>> "Address already in use" on bind().
>> 
>> 
>> When looking in Google there's a comprehensive looking
>> description of SO_REUSEADDR + SO_REUSEPORT across all the
>> different OS which insists that SO_REUSEPORT and SO_REUSEADDR
>> are functionally equivalent for multicast IP addresses:
>> 
>> https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ
>> 
>> And AFAIK, macOS should behave the same way, which suggests
>> this patch is not needed.
>> 
>> Oddly though, I don't find this in the FreeBSD man page - its
>> description seems fairly clear that SO_REUSEPORT is needed for
>> multicast
>> 
>> [quote]
>> SO_REUSEPORT allows completely duplicate bindings by multiple processes
>> if they all set SO_REUSEPORT before binding the port. This option
>> permits multiple instances of a program to each receive UDP/IP multicast
>> or broadcast datagrams destined for the bound port.
>> [/quote]
>> 
>> 
>>> 
>>> As per BSD manual pages binding to any address, even one not bound
>>> to any available network interface in the system, should be
>>> IP_BINDANY. Without binding to INADDR_ANY macOS will return
>>> "Can't assign requested address" on send().
>> 
>> I didn't find a quote about this in the FreeBSD man pages I looked
>> at, and it feels dubious to me. If the user gives QEMU a address to
>> bind to, we should surely be honouring that, not changing it to
>> INADDR_ANY.
>> 
>> If using INADDR_ANY though, thsi could explain the need for
>> SO_REUSEPORT, since INADDR_ANY is not a designated mcast address.
>> 
>>> Cc: Jason Wang <jasowang@redhat.com>
>>> Cc: Daniel P. Berrange <berrange@redhat.com>
>>> Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
>>> Signed-off-by: Vitaly Cheptsov <cheptsov@ispras.ru>
>>> ---
>>> net/socket.c | 18 ++++++++++++++++--
>>> 1 file changed, 16 insertions(+), 2 deletions(-)
>>> 
>>> diff --git a/net/socket.c b/net/socket.c
>>> index ea5220a2eb..8b2c6c4bb8 100644
>>> --- a/net/socket.c
>>> +++ b/net/socket.c
>>> @@ -252,10 +252,24 @@ static int net_socket_mcast_create(struct sockaddr_in *mcastaddr,
>>> goto fail;
>>> }
>>> 
>>> - ret = bind(fd, (struct sockaddr *)mcastaddr, sizeof(*mcastaddr));
>>> + val = 1;
>>> + ret = qemu_setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &val, sizeof(val));
>>> + if (ret < 0) {
>>> + error_setg_errno(errp, errno,
>>> + "can't set socket option SO_REUSEPORT");
>>> + goto fail;
>>> + }
>> 
>> AFAIK, this likely won't compile on Windows since it lacks SO_REUSEPORT
>> 
>>> +
>>> + struct sockaddr_in bindaddr;
>>> + memset(&bindaddr, 0, sizeof(bindaddr));
>>> + bindaddr.sin_family = AF_INET;
>>> + bindaddr.sin_addr.s_addr = htonl(INADDR_ANY);
>>> + bindaddr.sin_port = mcastaddr->sin_port;
>>> + ret = bind(fd, (struct sockaddr *)&bindaddr, sizeof(bindaddr));
>>> +
>>> if (ret < 0) {
>>> error_setg_errno(errp, errno, "can't bind ip=%s to socket",
>>> - inet_ntoa(mcastaddr->sin_addr));
>>> + inet_ntoa(bindaddr.sin_addr));
>>> goto fail;
>>> }
>> 
>> 
>> With regards,
>> Daniel
>> --
>> |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
>> |: https://libvirt.org -o- https://fstop138.berrange.com :|
>> |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
> 


[-- Attachment #2: Message signed with OpenPGP --]
[-- Type: application/pgp-signature, Size: 833 bytes --]