package/systemd: Backport fix for network-generator

The systemd-network-generator.service will fail to parse the bootarg "ip=xxx"
if it's missing the (optional) hostname field. Backport this fix from
systemd v245.

Signed-off-by: Brandon Maier <brandon.maier@rockwellcollins.com>
Reviewed-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/systemd/0003-network-generator-allow-empty-hostname.patch

@@ -0,0 +1,44 @@
+From 21a925a4ac7955e7d7e6cfd477e96d3a2aaee7db Mon Sep 17 00:00:00 2001
+From: Yu Watanabe <watanabe.yu+github@gmail.com>
+Date: Thu, 12 Dec 2019 19:01:21 +0900
+Subject: [PATCH 1/1] network-generator: allow empty hostname
+
+Fixes #14319.
+
+[Brandon: backport from https://github.com/systemd/systemd/commit/21a925a4ac7955e7d7e6cfd477e96d3a2aaee7db]
+Signed-off-by: Brandon Maier <brandon.maier@rockwellcollins.com>
+---
+ src/network/generator/network-generator.c | 10 ++++++----
+ 1 file changed, 6 insertions(+), 4 deletions(-)
+
+diff --git a/src/network/generator/network-generator.c b/src/network/generator/network-generator.c
+index 81afa95307..bed1e42697 100644
+--- a/src/network/generator/network-generator.c
++++ b/src/network/generator/network-generator.c
+@@ -574,7 +574,7 @@ static int parse_netmask_or_prefixlen(int family, const char **value, unsigned c
+ 
+ static int parse_cmdline_ip_address(Context *context, int family, const char *value) {
+         union in_addr_union addr = {}, peer = {}, gateway = {};
+-        const char *hostname, *ifname, *dhcp_type, *dns, *p;
++        const char *hostname = NULL, *ifname, *dhcp_type, *dns, *p;
+         unsigned char prefixlen;
+         int r;
+ 
+@@ -599,9 +599,11 @@ static int parse_cmdline_ip_address(Context *context, int family, const char *va
+         if (!p)
+                 return -EINVAL;
+ 
+-        hostname = strndupa(value, p - value);
+-        if (!hostname_is_valid(hostname, false))
+-                return -EINVAL;
++        if (p != value) {
++                hostname = strndupa(value, p - value);
++                if (!hostname_is_valid(hostname, false))
++                        return -EINVAL;
++        }
+ 
+         value = p + 1;
+ 
+-- 
+2.23.0
+