Subject: Aoe-sancheck: Refine interface probing
Origin: aoetools-36-11-g4a3ee18 <https://github.com/OpenAoE/aoetools/commit/aoetools-36-11-g4a3ee18>
Upstream-Author: Christoph Biedl <debian.axhn@manchmal.in-ulm.de>
Date: Sat May 22 14:37:25 2021 +0200

    There are two issues in the ethlist function in aoe-sancheck.c:

    First it skips all network interfaces that do not start with "eth". This
    is a problem these days where people use different naming schemes like the
    so-called predictable interface names as mandated by udev/systemd.

    Second it only probes for interfaces with an interface number of up
    to 15. At least in current Linux, that number can take huge values and
    those interfaces will be ignored completely.

    About the first: Probe all interfaces (but lo) that support the ARP
    protocol, assuming that is a fair indicator for ethernet support.

    About the second, use the if_nameindex function to get a list of all
    interfaces currently known to the kernel and operate on that one.

--- a/aoe-sancheck.c
+++ b/aoe-sancheck.c
@@ -501,23 +501,38 @@
 int
 ethlist(char **ifs, int nifs)
 {
-	int i, s, n;
+	int s, n;
 	struct ifreq ifr;
+	struct if_nameindex *if_ni, *i;
 
 	s = socket(AF_INET, SOCK_STREAM, 0);
 	if (s < 0)
 		return 0;
+
+	if_ni = if_nameindex();
+	if (if_ni == NULL)
+		return 0;
+
 	n = 0;
-	for (i=0; i<nifs; i++) {
+	for (i = if_ni; ! (i->if_index == 0 && i->if_name == NULL); i++) {
 		memset(&ifr, 0, sizeof ifr);
-		ifr.ifr_ifindex = i;
-		if (ioctl(s, SIOCGIFNAME, &ifr) < 0)
+		ifr.ifr_ifindex = i->if_index;
+		strcpy(ifr.ifr_name, i->if_name);
+		// get interface flags
+		if (ioctl(s, SIOCGIFFLAGS, &ifr) < 0)
+			continue;
+		// only use interfaces that use arp protocol
+		if (ifr.ifr_flags & IFF_NOARP)
 			continue;
-		if (strncmp(ifr.ifr_name, "eth", 3))
+		// skip loopback interfaces
+		if (ifr.ifr_flags & IFF_LOOPBACK)
 			continue;
+		if (n == nifs)
+			break;
 		inserteth(ifs, nifs, ifr.ifr_name);
 		n++;
 	}
+	if_freenameindex(if_ni);
 	close(s);
 	return n;
 }