From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Mon, 31 Jan 2022 10:26:51 +0000 (+0900)
Subject: network: do not remove localhost address
X-Git-Tag: v251-rc1~397^2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b69bfa43052586cd6894c32d7d3d447195539ec5;p=thirdparty%2Fsystemd.git

network: do not remove localhost address

Managing loopback interfaces by networkd is not recommended, but supporeted.
Even such spurious situation, do not drop the localhost addresses.
---

diff --git a/src/basic/in-addr-util.c b/src/basic/in-addr-util.c
index a43a8319912..660c1f18247 100644
--- a/src/basic/in-addr-util.c
+++ b/src/basic/in-addr-util.c
@@ -121,6 +121,19 @@ int in_addr_is_localhost(int family, const union in_addr_union *u) {
         return -EAFNOSUPPORT;
 }
 
+int in_addr_is_localhost_one(int family, const union in_addr_union *u) {
+        assert(u);
+
+        if (family == AF_INET)
+                /* 127.0.0.1 */
+                return be32toh(u->in.s_addr) == UINT32_C(0x7F000001);
+
+        if (family == AF_INET6)
+                return IN6_IS_ADDR_LOOPBACK(&u->in6); /* lgtm [cpp/potentially-dangerous-function] */
+
+        return -EAFNOSUPPORT;
+}
+
 bool in6_addr_is_ipv4_mapped_address(const struct in6_addr *a) {
         return a->s6_addr32[0] == 0 &&
                 a->s6_addr32[1] == 0 &&
diff --git a/src/basic/in-addr-util.h b/src/basic/in-addr-util.h
index 0178391e5f2..5de87a9539f 100644
--- a/src/basic/in-addr-util.h
+++ b/src/basic/in-addr-util.h
@@ -49,6 +49,7 @@ bool in6_addr_is_link_local_all_nodes(const struct in6_addr *a);
 
 bool in4_addr_is_localhost(const struct in_addr *a);
 int in_addr_is_localhost(int family, const union in_addr_union *u);
+int in_addr_is_localhost_one(int family, const union in_addr_union *u);
 
 bool in4_addr_is_local_multicast(const struct in_addr *a);
 bool in4_addr_is_non_local(const struct in_addr *a);
diff --git a/src/network/networkd-address.c b/src/network/networkd-address.c
index b5091bb5980..44f77db3be6 100644
--- a/src/network/networkd-address.c
+++ b/src/network/networkd-address.c
@@ -854,6 +854,10 @@ int link_drop_foreign_addresses(Link *link) {
                 if (address->family == AF_INET6 && in6_addr_is_link_local(&address->in_addr.in6))
                         continue;
 
+                /* Do not remove localhost address (127.0.0.1 and ::1) */
+                if (link->flags & IFF_LOOPBACK && in_addr_is_localhost_one(address->family, &address->in_addr) > 0)
+                        continue;
+
                 /* Ignore addresses we configured. */
                 if (address->source != NETWORK_CONFIG_SOURCE_FOREIGN)
                         continue;