netdev - Re: [PATCH net v2 2/6] vsock: Allow retrying on connect() failure

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Message-ID: <1b9e780c-033f-4801-ac8a-4ed6ba01656d@rbox.co>
Date: Wed, 22 Jan 2025 22:06:51 +0100
From: Michal Luczaj <mhal@...x.co>
To: Luigi Leonardi <leonardi@...hat.com>
Cc: Stefano Garzarella <sgarzare@...hat.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH net v2 2/6] vsock: Allow retrying on connect() failure

On 1/22/25 17:28, Luigi Leonardi wrote:
> On Tue, Jan 21, 2025 at 03:44:03PM +0100, Michal Luczaj wrote:
>> sk_err is set when a (connectible) connect() fails. Effectively, this makes
>> an otherwise still healthy SS_UNCONNECTED socket impossible to use for any
>> subsequent connection attempts.
>>
>> Clear sk_err upon trying to establish a connection.
>>
>> Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")
>> Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>
>> Signed-off-by: Michal Luczaj <mhal@...x.co>
>> ---
>> net/vmw_vsock/af_vsock.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> index cfe18bc8fdbe7ced073c6b3644d635fdbfa02610..075695173648d3a4ecbd04e908130efdbb393b41 100644
>> --- a/net/vmw_vsock/af_vsock.c
>> +++ b/net/vmw_vsock/af_vsock.c
>> @@ -1523,6 +1523,11 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
>> 		if (err < 0)
>> 			goto out;
>>
>> +		/* sk_err might have been set as a result of an earlier
>> +		 * (failed) connect attempt.
>> +		 */
>> +		sk->sk_err = 0;
>
> Just to understand: Why do you reset sk_error after calling to 
> transport->connect and not before?

transport->connect() can fail. In such case, I thought, it would be better
to keep the old value of sk_err. Otherwise we'd have an early failing
vsock_connect() that clears sk_err.

> My worry is that a transport might check this field and return an error.
> IIUC with virtio-based transports this is not the case.

Right, transport might check, but currently none of the transports do.