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

[Jon Maloy]

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 <lucien....@gmail.com>
---
  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;
+               }
+       }
+}

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