tcp: track zero rwnd errors

Type: feature

Distinguish between rcv window errors and errors after we advertised a
zero rcv window, i.e., potential window probes.

Change-Id: I6cb453c7aaae456c0a05a8328cfaa55eaca10bf7
Signed-off-by: Florin Coras <fcoras@cisco.com>

diff --git a/src/vnet/tcp/tcp_error.def b/src/vnet/tcp/tcp_error.def
index 7dbe952..5acc576 100644 (file)
--- a/src/vnet/tcp/tcp_error.def
+++ b/src/vnet/tcp/tcp_error.def
@@ -48,4 +48,5 @@ tcp_error (OPTIONS, "Could not parse options")
 tcp_error (PAWS, "PAWS check failed")
 tcp_error (RCV_WND, "Segment not in receive window")
 tcp_error (FIN_RCVD, "FINs received")
-tcp_error (LINK_LOCAL_RW, "No rewrite for link local connection")
\ No newline at end of file
+tcp_error (LINK_LOCAL_RW, "No rewrite for link local connection")
+tcp_error (ZERO_RWND, "Zero receive window")
\ No newline at end of file

diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c
index 0b1ac73..45a40a2 100755 (executable)
--- a/src/vnet/tcp/tcp_input.c
+++ b/src/vnet/tcp/tcp_input.c
@@ -365,6 +365,13 @@ tcp_segment_validate (tcp_worker_ctx_t * wrk, tcp_connection_t * tc0,
 
       *error0 = TCP_ERROR_RCV_WND;
 
+      /* If we advertised a zero rcv_wnd and the segment is in the past or the
+       * next one that we expect, it is probably a window probe */
+      if ((tc0->flags & TCP_CONN_ZERO_RWND_SENT)
+         && seq_lt (vnet_buffer (b0)->tcp.seq_end,
+                    tc0->rcv_las + tc0->rcv_opts.mss))
+       *error0 = TCP_ERROR_ZERO_RWND;
+
       tc0->errors.below_data_wnd += seq_lt (vnet_buffer (b0)->tcp.seq_end,
                                            tc0->rcv_las);