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-rw-r--r--src/network/networkd-link.c30
1 files changed, 28 insertions, 2 deletions
diff --git a/src/network/networkd-link.c b/src/network/networkd-link.c
index e4800a10de..bc363f95b0 100644
--- a/src/network/networkd-link.c
+++ b/src/network/networkd-link.c
@@ -1237,12 +1237,38 @@ static int link_enter_join_netdev(Link *link) {
static int link_set_ipv4_forward(Link *link) {
const char *p = NULL;
+ bool b;
int r;
+ b = link_ipv4_forward_enabled(link);
+
p = strappenda("/proc/sys/net/ipv4/conf/", link->ifname, "/forwarding");
- r = write_string_file_no_create(p, one_zero(link_ipv4_forward_enabled(link)));
+ r = write_string_file_no_create(p, one_zero(b));
if (r < 0)
- log_link_warning_errno(link, r, "Cannot configure IPv4 forwarding for interface: %m");
+ log_link_warning_errno(link, r, "Cannot configure IPv4 forwarding for interface %s: %m", link->ifname);
+
+ if (b) {
+ _cleanup_free_ char *buf = NULL;
+
+ /* If IP forwarding is turned on for this interface,
+ * then propagate this to the global setting. Given
+ * that turning this on has side-effects on other
+ * fields, we'll try to avoid doing this unless
+ * necessary, hence check the previous value
+ * first. Note that we never turn this option off
+ * again, since all interfaces we manage do not do
+ * forwarding anyway by default, and ownership rules
+ * of this control are so unclear. */
+
+ r = read_one_line_file("/proc/sys/net/ipv4/ip_forward", &buf);
+ if (r < 0)
+ log_link_warning_errno(link, r, "Cannot read /proc/sys/net/ipv4/ip_forward: %m");
+ else if (!streq(buf, "1")) {
+ r = write_string_file_no_create("/proc/sys/net/ipv4/ip_forward", "1");
+ if (r < 0)
+ log_link_warning_errno(link, r, "Cannot write /proc/sys/net/ipv4/ip_forward: %m");
+ }
+ }
return 0;
}