From 18195e7bb2407be74aef78beb43020e8a2e53b55 Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
Date: Thu, 21 Aug 2025 13:05:24 +0100
Subject: [PATCH] Useful error logging in dhcp-split-relay code.

---
 src/rfc2131.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/rfc2131.c b/src/rfc2131.c
index 3fc1a39..a15b78c 100644
--- a/src/rfc2131.c
+++ b/src/rfc2131.c
@@ -3114,7 +3114,11 @@ void relay_upstream4(struct in_addr iface_addr, int iface_index, struct dhcp_pac
 	    {
 	      /* get our address on the server-facing interface. */
 	      if (ioctl(daemon->dhcpfd, SIOCGIFADDR, &ifr) == -1)
-		continue;
+		{
+		  my_syslog(MS_DHCP | LOG_ERR, _("Cannot send to server via interface %s: %s"), relay->interface, strerror(errno));
+		  continue;
+		}
+	      
 	      relay->uplink.addr4 = ((struct sockaddr_in *) &ifr.ifr_addr)->sin_addr;
 	    }