logging_gsmtap: Temporarily disable logging when sending the logs

This avoids an infinite recursion when sending a gsmtap log message
causes a log message.
Temporarily set target->loglevel higher than LOGL_FATAL, which
effectively disables logging for that target. Other targets like stderr
will still log this message so there is still an indication that
something went wrong.

Change-Id: I19203cadbad6019a3834793b8ac816d903fe088e
Related: OS#6213
---
M src/core/logging_gsmtap.c
1 file changed, 22 insertions(+), 0 deletions(-)

diff --git a/src/core/logging_gsmtap.c b/src/core/logging_gsmtap.c
index dfd059b..7775c27 100644
--- a/src/core/logging_gsmtap.c
+++ b/src/core/logging_gsmtap.c
@@ -65,6 +65,7 @@
 	struct timeval tv;
 	int rc;
 	const char *file_basename;
+	unsigned int _level;
 
 	/* get timestamp ASAP */
 	osmo_gettimeofday(&tv, NULL);
@@ -114,7 +115,11 @@
 	}
 	msgb_put(msg, rc);
 
+	/* Ensure that any error occurring when sending the log message doesn't cause infinite recursion */
+	_level = target->loglevel;
+	target->loglevel = UINT8_MAX;
 	rc = gsmtap_sendmsg(target->tgt_gsmtap.gsmtap_inst, msg);
+	target->loglevel = _level;
 	if (rc)
 		msgb_free(msg);
 }

