From 067cc069aa2cfa204c7e33c58f017a804f568f8d Mon Sep 17 00:00:00 2001
From: JacobBarthelmeh <jacob@wolfssl.com>
Date: Mon, 7 Aug 2023 09:55:33 -0700
Subject: [PATCH] add check for full window with SSHD and improve nonblocking
 connect with client

---
 apps/wolfsshd/wolfsshd.c | 22 ++++++++++++++++++++--
 examples/client/client.c |  8 +++++++-
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/apps/wolfsshd/wolfsshd.c b/apps/wolfsshd/wolfsshd.c
index 4991b62dc..f014cc85e 100644
--- a/apps/wolfsshd/wolfsshd.c
+++ b/apps/wolfsshd/wolfsshd.c
@@ -704,6 +704,7 @@ static int SHELL_Subsystem(WOLFSSHD_CONNECTION* conn, WOLFSSH* ssh,
     byte shellBuffer[EXAMPLE_BUFFER_SZ];
     byte channelBuffer[EXAMPLE_BUFFER_SZ];
     char* forcedCmd;
+    int   windowFull = 0;
 
     forcedCmd = wolfSSHD_ConfigGetForcedCmd(usrConf);
 
@@ -876,7 +877,7 @@ static int SHELL_Subsystem(WOLFSSHD_CONNECTION* conn, WOLFSSH* ssh,
             pending = 1; /* found some pending SSH data */
         }
 
-        if (pending || FD_ISSET(sshFd, &readFds)) {
+        if (windowFull || pending || FD_ISSET(sshFd, &readFds)) {
             word32 lastChannel = 0;
 
             /* The following tries to read from the first channel inside
@@ -910,6 +911,19 @@ static int SHELL_Subsystem(WOLFSSHD_CONNECTION* conn, WOLFSSH* ssh,
             }
         }
 
+        /* if the window was previously full, try resending the data */
+        if (windowFull) {
+            cnt_w = wolfSSH_ChannelIdSend(ssh, shellChannelId,
+                    shellBuffer, cnt_r);
+            if (cnt_w == WS_WINDOW_FULL) {
+                windowFull = 1;
+                continue;
+            }
+            else {
+                windowFull = 0;
+            }
+        }
+
         if (FD_ISSET(childFd, &readFds)) {
             cnt_r = (int)read(childFd, shellBuffer, sizeof shellBuffer);
             /* This read will return 0 on EOF */
@@ -923,7 +937,11 @@ static int SHELL_Subsystem(WOLFSSHD_CONNECTION* conn, WOLFSSH* ssh,
                 if (cnt_r > 0) {
                     cnt_w = wolfSSH_ChannelIdSend(ssh, shellChannelId,
                             shellBuffer, cnt_r);
-                    if (cnt_w < 0)
+                    if (cnt_w == WS_WINDOW_FULL) {
+                        windowFull = 1;
+                        continue;
+                    }
+                    else if (cnt_w < 0)
                         break;
                 }
             }
diff --git a/examples/client/client.c b/examples/client/client.c
index 045fb4ff1..56eea6471 100644
--- a/examples/client/client.c
+++ b/examples/client/client.c
@@ -148,7 +148,13 @@ static int NonBlockSSH_connect(WOLFSSH* ssh)
             printf("... client would write block\n");
 
         select_ret = tcp_select(sockfd, 1);
-        if (select_ret == WS_SELECT_RECV_READY ||
+
+        /* Continue in want write cases even if did not select on socket
+         * because there could be pending data to be written. Added continue
+         * on want write for test cases where a forced want read was introduced
+         * and the socket will not be receiving more data. */
+        if (error == WS_WANT_WRITE || error == WS_WANT_READ ||
+            select_ret == WS_SELECT_RECV_READY ||
             select_ret == WS_SELECT_ERROR_READY)
         {
             ret = wolfSSH_connect(ssh);