[Devel] [PATCH RH7] sock: allow reading and changing sk_userlocks with setsockopt

[Alexander Mikhalitsyn]

On Thu, 29 Jul 2021 17:28:56 +0300
Pavel Tikhomirov <ptikhomirov at virtuozzo.com> wrote:

> SOCK_SNDBUF_LOCK and SOCK_RCVBUF_LOCK flags disable automatic socket
> buffers adjustment done by kernel (see tcp_fixup_rcvbuf() and
> tcp_sndbuf_expand()). If we've just created a new socket this adjustment
> is enabled on it, but if one changes the socket buffer size by
> setsockopt(SO_{SND,RCV}BUF*) it becomes disabled.
> 
> CRIU needs to call setsockopt(SO_{SND,RCV}BUF*) on each socket on
> restore as it first needs to increase buffer sizes for packet queues
> restore and second it needs to restore back original buffer sizes. So
> after CRIU restore all sockets become non-auto-adjustable, which can
> decrease network perfomance of dumped applications significantly.
> 
> CRIU need to be able to restore sockets with enabled/disabled adjustment
> to the same state it was before dump, so let's add special setsockopt
> for it.
> 
> Notes:
> - Use big number for SO_BUF_LOCK - 1072 in mainstream current available
> number is 72, but we better not use it to exclude later compatibility
> problems;
> - For several arch-es like alpha, mips, parisc and sparc we need to
> separately define setsockopt numbers, but as Virtuozzo is x86_64 only
> we can skip them.
> 
> https://jira.sw.ru/browse/PSBM-131580
> 
> Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>

Reviewed-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>

> ---
> This also need to go to VZ8 kernel.
> ---
>  include/uapi/asm-generic/socket.h |  2 ++
>  net/core/sock.c                   | 10 ++++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
> index aa97305f500e..39680b80dcd9 100644
> --- a/include/uapi/asm-generic/socket.h
> +++ b/include/uapi/asm-generic/socket.h
> @@ -84,4 +84,6 @@
>  
>  #define SCM_TIMESTAMPING_PKTINFO	58
>  
> +#define SO_BUF_LOCK		1072
> +
>  #endif /* __ASM_GENERIC_SOCKET_H */
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 44e91c8c0f0a..0b2f95de7494 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1029,6 +1029,13 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
>  					 sk->sk_max_pacing_rate);
>  		break;
>  
> +	case SO_BUF_LOCK:
> +		val = val & (SOCK_SNDBUF_LOCK | SOCK_RCVBUF_LOCK);
> +		sk->sk_userlocks = (sk->sk_userlocks &
> +				    ~(SOCK_SNDBUF_LOCK | SOCK_RCVBUF_LOCK))
> +				   | val;
> +		break;
> +
>  	default:
>  		ret = -ENOPROTOOPT;
>  		break;
> @@ -1285,6 +1292,9 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
>  	case SO_MAX_PACING_RATE:
>  		v.val = sk->sk_max_pacing_rate;
>  		break;
> +	case SO_BUF_LOCK:
> +		v.val = sk->sk_userlocks & (SOCK_SNDBUF_LOCK | SOCK_RCVBUF_LOCK);
> +		break;
>  
>  	default:
>  		return -ENOPROTOOPT;
> -- 
> 2.31.1
> 
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