From a973a6e10ef9d978491733e56723b4a8e078959f Mon Sep 17 00:00:00 2001
From: Adam Ierymenko <adam.ierymenko@zerotier.com>
Date: Thu, 8 Oct 2020 12:04:57 -0400
Subject: [PATCH] Leave feth devices over feth10000 alone.

---
 osdep/MacEthernetTap.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/osdep/MacEthernetTap.cpp b/osdep/MacEthernetTap.cpp
index bc5a6710d..1e538e883 100644
--- a/osdep/MacEthernetTap.cpp
+++ b/osdep/MacEthernetTap.cpp
@@ -110,7 +110,9 @@ MacEthernetTap::MacEthernetTap(
 		if (!getifaddrs(&ifa)) {
 			struct ifaddrs *p = ifa;
 			while (p) {
-				if ((!strncmp(p->ifa_name,"feth",4))&&(strlen(p->ifa_name) >= 7)&&(deleted.count(std::string(p->ifa_name)) == 0)) {
+				int nameLen = (int)strlen(p->ifa_name);
+				// Delete feth# from feth0 to feth9999, but don't touch >10000.
+				if ((!strncmp(p->ifa_name,"feth",4))&&(nameLen >= 5)&&(nameLen < 9)&&(deleted.count(std::string(p->ifa_name)) == 0)) {
 					deleted.insert(std::string(p->ifa_name));
 					const char *args[4];
 					args[0] = "/sbin/ifconfig";