[Buildroot] [PATCH] package/libssh: add patch to fix regression

[Heiko Thiery <heiko.thiery@gmail.com>]

The libssh server is used by libnetconf2. With libssh version 0.9.4 a
regression was introduced that wrongly leads to session closed after the
poll timeout.

The patch comes from upstrem:
https://git.libssh.org/projects/libssh.git/commit/?id=6417f5a3cac8537ac6f6ff7fc1642dfaa0917fb4

Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
---
 ...eturning-SSH_AGAIN-from-ssh_channel_.patch | 45 +++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 package/libssh/0002-channels-Avoid-returning-SSH_AGAIN-from-ssh_channel_.patch

diff --git a/package/libssh/0002-channels-Avoid-returning-SSH_AGAIN-from-ssh_channel_.patch b/package/libssh/0002-channels-Avoid-returning-SSH_AGAIN-from-ssh_channel_.patch
new file mode 100644
index 0000000000..9cc9389479
--- /dev/null
+++ b/package/libssh/0002-channels-Avoid-returning-SSH_AGAIN-from-ssh_channel_.patch
@@ -0,0 +1,45 @@
+From 6417f5a3cac8537ac6f6ff7fc1642dfaa0917fb4 Mon Sep 17 00:00:00 2001
+From: Jakub Jelen <jjelen@redhat.com>
+Date: Thu, 16 Apr 2020 11:13:34 +0200
+Subject: [PATCH] channels: Avoid returning SSH_AGAIN from
+ ssh_channel_poll_timeout()
+
+This addresses a regression introduced in 3bad0607, partially fixed in 022409e9,
+but the function was still able to return SSH_AGAIN, which was not expected by
+callers.
+
+Based on discussion in [1] and [2]
+
+[1] https://gitlab.com/libssh/libssh-mirror/-/merge_requests/101
+[2] https://www.libssh.org/archive/libssh/2020-03/0000029.html
+
+Signed-off-by: Jakub Jelen <jjelen@redhat.com>
+Reviewed-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
+
+[Backport from upstream commit:
+6417f5a3cac8537ac6f6ff7fc1642dfaa0917fb4]
+Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
+---
+ src/channels.c | 6 ++++++
+ 1 file changed, 6 insertions(+)
+
+diff --git a/src/channels.c b/src/channels.c
+index bcc1c207..9fe309d0 100644
+--- a/src/channels.c
++++ b/src/channels.c
+@@ -3116,6 +3116,12 @@ int ssh_channel_poll_timeout(ssh_channel channel, int timeout, int is_stderr)
+         session->session_state == SSH_SESSION_STATE_ERROR) {
+         rc = SSH_ERROR;
+         goto out;
++    } else if (rc == SSH_AGAIN) {
++        /* If the above timeout expired, it is ok and we do not need to
++         * attempt to check the read buffer. The calling functions do not
++         * expect us to return SSH_AGAIN either here. */
++        rc = SSH_OK;
++        goto out;
+     }
+     len = ssh_buffer_get_len(stdbuf);
+     if (len > 0) {
+-- 
+2.20.1
+
-- 
2.20.1