From: Jonathan Matthew <jonathan@d14n.org>
Subject: dhcp6leased frontend memory leak
To: tech@openbsd.org
Cc: florian@openbsd.org
Date: Thu, 19 Jun 2025 08:08:39 +1000

While looking at memory usage on my home router, I noticed the dhcp6leased 
frontend process had grown to around 170MB in the couple of months it had
been running.

After restarting with malloc leak checking and letting it run for a while,
the malloc dump reported that a number of allocations from getifaddrs()
hadn't been freed.

update_iface() calls getifaddrs() and then returns early without calling
freeifaddrs() in some conditions, one of which I'm hitting - it gets
called for lo1, which isn't in the frontend's interface list.
Not sure what that means.  My config is just
'request prefix delegation on dwqe0 for { lo1 vport0 vport1 }'.

Anyway, update_iface() doesn't look at the interface list until after
those checks are done, so we can just move the getifaddrs call down.
I've been running with this diff for a bit and the steady growth of
the frontend process (8-12 kB every 5 minutes) is no longer happening.

ok?

Index: frontend.c
===================================================================
RCS file: /cvs/src/sbin/dhcp6leased/frontend.c,v
diff -u -p -u -p -r1.21 frontend.c
--- frontend.c	27 Apr 2025 16:22:33 -0000	1.21
+++ frontend.c	18 Jun 2025 10:39:52 -0000
@@ -559,9 +559,6 @@ update_iface(uint32_t if_index)
 	int			 flags;
 	char			 ifnamebuf[IF_NAMESIZE], *if_name;
 
-	if (getifaddrs(&ifap) != 0)
-		fatal("getifaddrs");
-
 	if ((if_name = if_indextoname(if_index, ifnamebuf)) == NULL)
 		return;
 
@@ -570,6 +567,9 @@ update_iface(uint32_t if_index)
 
 	if (find_iface_conf(&frontend_conf->iface_list, if_name) == NULL)
 		return;
+
+	if (getifaddrs(&ifap) != 0)
+		fatal("getifaddrs");
 
 	memset(&ifinfo, 0, sizeof(ifinfo));
 	ifinfo.if_index = if_index;