Re: [tipc-discussion] [PATCH net-next] tipc: return POLLOUT for sockets in an unconnected state

[Ying X. <yin...@wi...>]

Erik Hugne wrote:
> If an implied connect is attempted during link congestion,
> the connect message will be discarded and sendmsg will return
> EAGAIN. The application then need to retry the connection attempt
> after congestion have abated.
> This fixes a problem where polling on a socket in an
> unconnected state always returned a zero mask.
>
> Signed-off-by: Erik Hugne <eri...@er...>
> ---
>  net/tipc/socket.c |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/net/tipc/socket.c b/net/tipc/socket.c
> index 03a2610..7710145 100644
> --- a/net/tipc/socket.c
> +++ b/net/tipc/socket.c
> @@ -407,7 +407,7 @@ static int get_name(struct socket *sock, struct sockaddr *uaddr,
>   * socket state		flags set
>   * ------------		---------
>   * unconnected		no read flags
> - *			no write flags
> + *			POLLOUT if port is not congested
>   *
>   * connecting		POLLIN/POLLRDNORM if ACK/NACK in rx queue
>   *			no write flags
> @@ -437,6 +437,10 @@ static unsigned int poll(struct file *file, struct socket *sock,
>  	poll_wait(file, sk_sleep(sk), wait);
>  
>  	switch ((int)sock->state) {
> +	case SS_UNCONNECTED:
> +		if (!tipc_sk_port(sk)->congested)
> +			mask |= POLLOUT;
> +		break;
>   

Maybe there has some potential issue, please see below scenario:

1. fd = socket(SOCK_STREAM)-->tipc_create() //sock->state = SS_UNCONNECTED
2. poll(fd)

Each time the poll() is timed out, the POLLOUT event will be returned to 
poll() even if any message *doesn't* be sent via the socket.

So please confirm the case.

Thanks,
Ying

>  	case SS_READY:
>  	case SS_CONNECTED:
>  		if (!tipc_sk_port(sk)->congested)
>