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Posted to commits@nuttx.apache.org by "michallenc (via GitHub)" <gi...@apache.org> on 2025/07/07 19:33:52 UTC
[I] [FEATURE] Polling support for Unix datagram sockets [nuttx]
michallenc opened a new issue, #16688:
URL: https://github.com/apache/nuttx/issues/16688
### Is your feature request related to a problem? Please describe.
This is a followup of [!16555](https://github.com/apache/nuttx/issues/16555) that solved the issue of non working DGRAM sockets.
### Describe the solution you'd like
Polling for Unix datagram sockets (`SOCK_DGRAM`) is currently not implemented. The implementation to `local_netpoll.c` seems pretty straightforward (at least for `POLLIN`), just create receiver if it doesn't exist (default state for the datagram, basically the same as in `psock_dgram_recvfrom` and call `file_poll`. The behavior of poll is still not as expected though, because it returns `POLLHUP` right after the poll is called. But this event should not return on datagram sockets as they are not connection oriented.
This bring us back to the same issue @Cynerd already faced with stream sockets in https://github.com/apache/nuttx/pull/14667. NuttX sockets are implemented with fifos and pipes, but the expected behavior of local sockets (both stream and dgram) is a bit different from pipes.
```diff
diff --git a/net/local/local_netpoll.c b/net/local/local_netpoll.c
index e68833aa9a..264c59c28a 100644
--- a/net/local/local_netpoll.c
+++ b/net/local/local_netpoll.c
@@ -161,7 +161,29 @@ int local_pollsetup(FAR struct socket *psock, FAR struct pollfd *fds)
if (conn->lc_proto == SOCK_DGRAM)
{
- return -ENOSYS;
+ if (conn->lc_infile.f_inode == NULL)
+ {
+ ret = local_create_halfduplex(conn, conn->lc_path, conn->lc_rcvsize);
+ if (ret < 0)
+ {
+ nerr("ERROR: Failed to create FIFO for %s: %d\n",
+ conn->lc_path, ret);
+ return ret;
+ }
+
+ /* Open the receiving side of the transfer */
+
+ ret = local_open_receiver(conn, false);
+ if (ret < 0)
+ {
+ nerr("ERROR: Failed to open FIFO for %s: %d\n",
+ conn->lc_path, ret);
+ local_release_halfduplex(conn);
+ return ret;
+ }
+ }
+
+ return file_poll(&conn->lc_infile, fds, true);
}
#ifdef CONFIG_NET_LOCAL_STREAM
@@ -310,7 +332,7 @@ int local_pollteardown(FAR struct socket *psock, FAR struct pollfd *fds)
if (conn->lc_proto == SOCK_DGRAM)
{
- return -ENOSYS;
+ return file_poll(&conn->lc_infile, fds, false);
}
#ifdef CONFIG_NET_LOCAL_STREAM
```
The implementation of polling for DGRAM would probably require the rewrite of local sockets and reimplementation with internet socket code base instead of fifos/pipes.
### Describe alternatives you've considered
_No response_
### Verification
- [x] I have verified before submitting the report.
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Re: [I] [FEATURE] Polling support for Unix datagram sockets [nuttx]
Posted by "michallenc (via GitHub)" <gi...@apache.org>.
michallenc commented on issue #16688:
URL: https://github.com/apache/nuttx/issues/16688#issuecomment-3047497191
Yeah, I know. I will likely get to this eventually, because it would be nice to have basic IPC with Unix datagrams, but it's not a priority.
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Re: [I] [FEATURE] Polling support for Unix datagram sockets [nuttx]
Posted by "xiaoxiang781216 (via GitHub)" <gi...@apache.org>.
xiaoxiang781216 commented on issue #16688:
URL: https://github.com/apache/nuttx/issues/16688#issuecomment-3047309283
> ### Is your feature request related to a problem? Please describe.
>
> This is a followup of [!16555](https://github.com/apache/nuttx/issues/16555) that solved the issue of non working DGRAM sockets.
> ### Describe the solution you'd like
>
> Polling for Unix datagram sockets (`SOCK_DGRAM`) is currently not implemented. The implementation to `local_netpoll.c` seems pretty straightforward (at least for `POLLIN`), just create receiver if it doesn't exist (default state for the datagram, basically the same as in `psock_dgram_recvfrom` and call `file_poll`. The behavior of poll is still not as expected though, because it returns `POLLHUP` right after the poll is called. But this event should not return on datagram sockets as they are not connection oriented.
>
we can hack fifo/pipe to change the behavior a little bit, actually the hook already exist:
https://github.com/apache/nuttx/blob/master/include/nuttx/fs/ioctl.h#L488-L493
> This bring us back to the same issue [@Cynerd](https://github.com/Cynerd) already faced with stream sockets in [#14667](https://github.com/apache/nuttx/pull/14667). NuttX sockets are implemented with fifos and pipes, but the expected behavior of local sockets (both stream and dgram) is a bit different from pipes.
> The implementation of polling for DGRAM would probably require the rewrite of local sockets and reimplementation with internet socket code base instead of fifos/pipes.
this method need rewrite the whole local socket which is a huge work.
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