Re: [tipc-discussion] [PATCH net-next 5/8] tipc: add probe recv and state transition

[Jon M. <jm...@re...>]

On 06/07/2021 14:22, Xin Long wrote:
> This patch is to receive and process the probe ack by checking
> msg_max_pkt() == l->pl.probe_size then does state transition
> in tipc_link_pl_recv().
> 
> For the details, see:
> 
>    https://lwn.net/Articles/860385/
> 
> Signed-off-by: Xin Long <luc...@gm...>
> ---
>   net/tipc/link.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 48 insertions(+)
> 
> diff --git a/net/tipc/link.c b/net/tipc/link.c
> index 3af6c04f82c2..241c9378e258 100644
> --- a/net/tipc/link.c
> +++ b/net/tipc/link.c
> @@ -293,6 +293,7 @@ static int tipc_link_advance_transmq(struct tipc_link *l, struct tipc_link *r,
>   static void tipc_link_update_cwin(struct tipc_link *l, int released,
>   				  bool retransmitted);
>   static void tipc_link_pl_send(struct tipc_link *l);
> +static void tipc_link_pl_recv(struct tipc_link *l);
>   /*
>    *  Simple non-static link routines (i.e. referenced outside this file)
>    */
> @@ -2333,6 +2334,13 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
>   			break;
>   		}
>   
> +		if (!reply && msg_max_pkt(hdr) == l->pl.probe_size) {
> +			tipc_link_pl_recv(l);
> +			if (l->pl.state == TIPC_PL_COMPLETE)
> +				break;
> +			tipc_link_build_proto_msg(l, STATE_MSG, PROBE_PLPMTU, 0, 0, 0, 0, xmitq);
> +		}
> +
>   		/* Receive Gap ACK blocks from peer if any */
>   		glen = tipc_get_gap_ack_blks(&ga, l, hdr, true);
>   
> @@ -3061,3 +3069,43 @@ static void tipc_link_pl_send(struct tipc_link *l)
>   	}
>   	l->pl.count = TIPC_PROBE_INTERVAL;
>   }
> +
> +static void tipc_link_pl_recv(struct tipc_link *l)
> +{
> +	pr_debug("%s: PLPMTUD: link: %p, state: %d, pmtu: %d, size: %d, high: %d\n",
> +		 __func__, l, l->pl.state, l->pl.pmtu, l->pl.probe_size, l->pl.probe_high);

Many of these lines will not pass checkpatch.
///jon

> +
> +	l->pl.pmtu = l->pl.probe_size;
> +	l->pl.count = 0;
> +	if (l->pl.state == TIPC_PL_BASE) {
> +		l->pl.state = TIPC_PL_SEARCH; /* Base -> Search */
> +		l->pl.probe_size += TIPC_PL_BIG_STEP;
> +	} else if (l->pl.state == TIPC_PL_ERROR) {
> +		l->pl.state = TIPC_PL_SEARCH; /* Error -> Search */
> +
> +		l->pl.pmtu = l->pl.probe_size;
> +		l->mtu = l->pl.pmtu;
> +		l->pl.probe_size += TIPC_PL_BIG_STEP;
> +	} else if (l->pl.state == TIPC_PL_SEARCH) {
> +		if (!l->pl.probe_high) {
> +			l->pl.probe_size = min(l->pl.probe_size + TIPC_PL_BIG_STEP,
> +					       TIPC_MAX_PLPMTU);
> +			return;
> +		}
> +		l->pl.probe_size += TIPC_PL_MIN_STEP;
> +		if (l->pl.probe_size >= l->pl.probe_high) {
> +			l->pl.probe_high = 0;
> +			l->pl.raise = 0;
> +			l->pl.state = TIPC_PL_COMPLETE; /* Search -> Search Complete */
> +
> +			l->pl.probe_size = l->pl.pmtu;
> +			l->mtu = l->pl.pmtu;
> +		}
> +	} else if (l->pl.state == TIPC_PL_COMPLETE) {
> +		l->pl.raise++;
> +		if (l->pl.raise == 30) {
> +			l->pl.state = TIPC_PL_SEARCH; /* Search Complete -> Search */
> +			l->pl.probe_size += TIPC_PL_MIN_STEP;
> +		}
> +	}
> +}
>