From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Mon, 18 Feb 2019 15:00:15 +0900
Subject: network: check whether ipv6 is enabled in sysctl

Currently, the value is read only once.

Fixes #11711.

(cherry picked from commit 4b600505dda8af6c43496f9e93e420a192d9a38b)
---
 src/network/networkd-link.c    | 12 ++++++++++++
 src/network/networkd-manager.c | 18 ++++++++++++++++++
 src/network/networkd-manager.h |  4 ++++
 3 files changed, 34 insertions(+)

diff --git a/src/network/networkd-link.c b/src/network/networkd-link.c
index 22392d7..322e701 100644
--- a/src/network/networkd-link.c
+++ b/src/network/networkd-link.c
@@ -51,6 +51,9 @@ static bool link_dhcp6_enabled(Link *link) {
         if (!link->network)
                 return false;
 
+        if (manager_sysctl_ipv6_enabled(link->manager) == 0)
+                return false;
+
         return link->network->dhcp & ADDRESS_FAMILY_IPV6;
 }
 
@@ -108,6 +111,9 @@ static bool link_ipv6ll_enabled(Link *link) {
         if (streq_ptr(link->kind, "wireguard"))
                 return false;
 
+        if (manager_sysctl_ipv6_enabled(link->manager) == 0)
+                return false;
+
         return link->network->link_local & ADDRESS_FAMILY_IPV6;
 }
 
@@ -120,6 +126,9 @@ static bool link_ipv6_enabled(Link *link) {
         if (link->network->bridge)
                 return false;
 
+        if (manager_sysctl_ipv6_enabled(link->manager) == 0)
+                return false;
+
         /* DHCPv6 client will not be started if no IPv6 link-local address is configured. */
         return link_ipv6ll_enabled(link) || network_has_static_ipv6_addresses(link->network);
 }
@@ -199,6 +208,9 @@ static bool link_ipv6_forward_enabled(Link *link) {
         if (link->network->ip_forward == _ADDRESS_FAMILY_BOOLEAN_INVALID)
                 return false;
 
+        if (manager_sysctl_ipv6_enabled(link->manager) == 0)
+                return false;
+
         return link->network->ip_forward & ADDRESS_FAMILY_IPV6;
 }
 
diff --git a/src/network/networkd-manager.c b/src/network/networkd-manager.c
index c8d369e..f32bc7f 100644
--- a/src/network/networkd-manager.c
+++ b/src/network/networkd-manager.c
@@ -23,6 +23,7 @@
 #include "path-util.h"
 #include "set.h"
 #include "strv.h"
+#include "sysctl-util.h"
 #include "tmpfile-util.h"
 #include "virt.h"
 
@@ -1360,6 +1361,8 @@ int manager_new(Manager **ret) {
         if (!m->state_file)
                 return -ENOMEM;
 
+        m->sysctl_ipv6_enabled = -1;
+
         r = sd_event_default(&m->event);
         if (r < 0)
                 return r;
@@ -1858,3 +1861,18 @@ int manager_request_product_uuid(Manager *m, Link *link) {
 
         return 0;
 }
+
+int manager_sysctl_ipv6_enabled(Manager *manager) {
+        _cleanup_free_ char *value = NULL;
+        int r;
+
+        if (manager->sysctl_ipv6_enabled >= 0)
+                return manager->sysctl_ipv6_enabled;
+
+        r = sysctl_read_ip_property(AF_INET6, "all", "disable_ipv6", &value);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to read net.ipv6.conf.all.disable_ipv6 sysctl property: %m");
+
+        manager->sysctl_ipv6_enabled = value[0] == '0';
+        return manager->sysctl_ipv6_enabled;
+}
diff --git a/src/network/networkd-manager.h b/src/network/networkd-manager.h
index 289ca96..d292d76 100644
--- a/src/network/networkd-manager.h
+++ b/src/network/networkd-manager.h
@@ -58,6 +58,8 @@ struct Manager {
         Set *rules;
         Set *rules_foreign;
         Set *rules_saved;
+
+        int sysctl_ipv6_enabled;
 };
 
 extern const sd_bus_vtable manager_vtable[];
@@ -95,4 +97,6 @@ Link *manager_dhcp6_prefix_get(Manager *m, struct in6_addr *addr);
 int manager_dhcp6_prefix_add(Manager *m, struct in6_addr *addr, Link *link);
 int manager_dhcp6_prefix_remove_all(Manager *m, Link *link);
 
+int manager_sysctl_ipv6_enabled(Manager *manager);
+
 DEFINE_TRIVIAL_CLEANUP_FUNC(Manager*, manager_free);