From 07a7441a1c0c09b63bb76fa48d540f8d37db0c6f Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 5 Mar 2021 20:33:15 +0100
Subject: [PATCH] socket-util: refuse "all" and "default" as valid ifnames

Let's avoid collisions with special sysctls.
---
 src/basic/socket-util.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
index 8267988ad9..06387bdfd6 100644
--- a/src/basic/socket-util.c
+++ b/src/basic/socket-util.c
@@ -736,6 +736,11 @@ bool ifname_valid_full(const char *p, IfnameValidFlags flags) {
         if (dot_or_dot_dot(p))
                 return false;
 
+        /* Let's refuse "all" and "default" as interface name, to avoid collisions with the special sysctl
+         * directories /proc/sys/net/{ipv4,ipv6}/conf/{all,default} */
+        if (STR_IN_SET(p, "all", "default"))
+                return false;
+
         for (const char *t = p; *t; t++) {
                 if ((unsigned char) *t >= 127U)
                         return false;