[CRIU] [PATCH] tcp: add ability to set a timestamp offset

[Pavel Emelyanov]

On 01/22/2013 04:20 PM, Andrey Vagin wrote:
> If a TCP socket will get live-migrated from one box to another the
> timestamps (which are typically ON) will get screwed up -- the new
> kernel will generate TS values that has nothing to do with what they
> were on dump. The solution is to yet again fix the kernel and put a
> "timestamp offset" on a socket.

Looks good to me.

> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  include/linux/tcp.h      | 2 ++
>  include/uapi/linux/tcp.h | 1 +
>  net/ipv4/tcp.c           | 6 ++++++
>  net/ipv4/tcp_output.c    | 7 ++++---
>  4 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> index 4e1d228..746dad5 100644
> --- a/include/linux/tcp.h
> +++ b/include/linux/tcp.h
> @@ -162,6 +162,8 @@ struct tcp_sock {
>  	u32	rcv_tstamp;	/* timestamp of last received ACK (for keepalives) */
>  	u32	lsndtime;	/* timestamp of last sent data packet (for restart window) */
>  
> +	u32	snd_tsval_offset; /* offset for snd_tsval */
> +
>  	struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
>  	unsigned long	tsq_flags;
>  
> diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> index e962faa..6b1ead0 100644
> --- a/include/uapi/linux/tcp.h
> +++ b/include/uapi/linux/tcp.h
> @@ -111,6 +111,7 @@ enum {
>  #define TCP_QUEUE_SEQ		21
>  #define TCP_REPAIR_OPTIONS	22
>  #define TCP_FASTOPEN		23	/* Enable FastOpen on listeners */
> +#define TCP_TIMESTAMP		24
>  
>  struct tcp_repair_opt {
>  	__u32	opt_code;
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 1ca2536..72dee28 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -2704,6 +2704,9 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
>  		else
>  			err = -EINVAL;
>  		break;
> +	case TCP_TIMESTAMP:
> +		tp->snd_tsval_offset = val - tcp_time_stamp;
> +		break;
>  	default:
>  		err = -ENOPROTOOPT;
>  		break;
> @@ -2952,6 +2955,9 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
>  	case TCP_USER_TIMEOUT:
>  		val = jiffies_to_msecs(icsk->icsk_user_timeout);
>  		break;
> +	case TCP_TIMESTAMP:
> +		val = tcp_time_stamp + tp->snd_tsval_offset;
> +		break;
>  	default:
>  		return -ENOPROTOOPT;
>  	}
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 5d45159..9b6d485 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -622,7 +622,7 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
>  
>  	if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
>  		opts->options |= OPTION_TS;
> -		opts->tsval = TCP_SKB_CB(skb)->when;
> +		opts->tsval = TCP_SKB_CB(skb)->when + tp->snd_tsval_offset;
>  		opts->tsecr = tp->rx_opt.ts_recent;
>  		remaining -= TCPOLEN_TSTAMP_ALIGNED;
>  	}
> @@ -705,6 +705,7 @@ static unsigned int tcp_synack_options(struct sock *sk,
>  				   struct tcp_extend_values *xvp,
>  				   struct tcp_fastopen_cookie *foc)
>  {
> +	struct tcp_sock *tp = tcp_sk(sk);
>  	struct inet_request_sock *ireq = inet_rsk(req);
>  	unsigned int remaining = MAX_TCP_OPTION_SPACE;
>  	u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ?
> @@ -739,7 +740,7 @@ static unsigned int tcp_synack_options(struct sock *sk,
>  	}
>  	if (likely(ireq->tstamp_ok)) {
>  		opts->options |= OPTION_TS;
> -		opts->tsval = TCP_SKB_CB(skb)->when;
> +		opts->tsval = TCP_SKB_CB(skb)->when + tp->snd_tsval_offset;
>  		opts->tsecr = req->ts_recent;
>  		remaining -= TCPOLEN_TSTAMP_ALIGNED;
>  	}
> @@ -806,7 +807,7 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
>  
>  	if (likely(tp->rx_opt.tstamp_ok)) {
>  		opts->options |= OPTION_TS;
> -		opts->tsval = tcb ? tcb->when : 0;
> +		opts->tsval = tcb ? tcb->when + tp->snd_tsval_offset : 0;
>  		opts->tsecr = tp->rx_opt.ts_recent;
>  		size += TCPOLEN_TSTAMP_ALIGNED;
>  	}
>