From f4fcc355bfeb2a0a71d36db0521ea045889d381b Mon Sep 17 00:00:00 2001
From: nullobsi <me@nullob.si>
Date: Tue, 8 Jul 2025 20:36:53 +0000
Subject: [PATCH] fix: only query valid FDs (#21)

On hardened glibc, calling FD_ISSET with an FD <0 or >FD_SETSIZE causes
a SIGABRT. Only query FDs that are associated with enabled repeater
modules to work around this crash.
---
 QnetGateway.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/QnetGateway.cpp b/QnetGateway.cpp
index 6801304..f08f0e3 100644
--- a/QnetGateway.cpp
+++ b/QnetGateway.cpp
@@ -2127,7 +2127,7 @@ void CQnetGateway::Run()
 		// process packets coming from local repeater module(s)
 		for (int i=0; i<3; i++)
 		{
-			if (keep_running && FD_ISSET(FromModem[i].GetFD(), &fdset))
+			if (keep_running && Rptr.mod[i].defined && FD_ISSET(FromModem[i].GetFD(), &fdset))
 			{
 				SDSVT dsvt;
 				const ssize_t len = FromModem[i].Read(dsvt.title, 56);