extend sysctl functions to shadow values

Pass to all the sysctl_* functions a hashmap which can be used to
optionally save the value written in the sysctl.

src/basic/sysctl-util.c

@@ -44,8 +44,39 @@ char* sysctl_normalize(char *s) {
         return s;
 }
 
-int sysctl_write(const char *property, const char *value) {
+static int shadow_update(Hashmap **shadow, const char *property, const char *value) {
+        _cleanup_free_ char *k = NULL, *v = NULL, *cur_k = NULL, *cur_v = NULL;
+        int r;
+
+        assert(property);
+        assert(value);
+
+        if (!shadow)
+                return 0;
+
+        k = strdup(property);
+        if (!k)
+                return -ENOMEM;
+
+        v = strdup(value);
+        if (!v)
+                return -ENOMEM;
+
+        cur_v = hashmap_remove2(*shadow, k, (void**)&cur_k);
+
+        r = hashmap_ensure_put(shadow, &path_hash_ops_free_free, k, v);
+        if (r < 0)
+                return r;
+
+        TAKE_PTR(k);
+        TAKE_PTR(v);
+
+        return 0;
+}
+
+int sysctl_write_full(const char *property, const char *value, Hashmap **shadow) {
         char *p;
+        int r;
 
         assert(property);
         assert(value);
@@ -58,6 +89,10 @@ int sysctl_write(const char *property, const char *value) {
 
         log_debug("Setting '%s' to '%s'", p, value);
 
+        r = shadow_update(shadow, p, value);
+        if (r < 0)
+                return r;
+
         return write_string_file(p, value, WRITE_STRING_FILE_VERIFY_ON_FAILURE | WRITE_STRING_FILE_DISABLE_BUFFER | WRITE_STRING_FILE_SUPPRESS_REDUNDANT_VIRTUAL);
 }
 
@@ -76,7 +111,7 @@ int sysctl_writef(const char *property, const char *format, ...) {
         return sysctl_write(property, v);
 }
 
-int sysctl_write_ip_property(int af, const char *ifname, const char *property, const char *value) {
+int sysctl_write_ip_property(int af, const char *ifname, const char *property, const char *value, Hashmap **shadow) {
         const char *p;
 
         assert(property);
@@ -93,10 +128,10 @@ int sysctl_write_ip_property(int af, const char *ifname, const char *property, c
         } else
                 p = strjoina("net/", af_to_ipv4_ipv6(af), "/", property);
 
-        return sysctl_write(p, value);
+        return sysctl_write_full(p, value, shadow);
 }
 
-int sysctl_write_ip_neighbor_property(int af, const char *ifname, const char *property, const char *value) {
+int sysctl_write_ip_neighbor_property(int af, const char *ifname, const char *property, const char *value, Hashmap **shadow) {
         const char *p;
 
         assert(property);
@@ -113,7 +148,7 @@ int sysctl_write_ip_neighbor_property(int af, const char *ifname, const char *pr
         } else
                 p = strjoina("net/", af_to_ipv4_ipv6(af), "/neigh/default/", property);
 
-        return sysctl_write(p, value);
+        return sysctl_write_full(p, value, shadow);
 }
 
 int sysctl_read(const char *property, char **ret) {

src/basic/sysctl-util.h

@@ -10,27 +10,30 @@
 
 char* sysctl_normalize(char *s);
 int sysctl_read(const char *property, char **value);
-int sysctl_write(const char *property, const char *value);
+int sysctl_write_full(const char *property, const char *value, Hashmap **shadow);
 int sysctl_writef(const char *property, const char *format, ...) _printf_(2, 3);
-
-int sysctl_read_ip_property(int af, const char *ifname, const char *property, char **ret);
-int sysctl_write_ip_property(int af, const char *ifname, const char *property, const char *value);
-static inline int sysctl_write_ip_property_boolean(int af, const char *ifname, const char *property, bool value) {
-        return sysctl_write_ip_property(af, ifname, property, one_zero(value));
+static inline int sysctl_write(const char *property, const char *value) {
+        return sysctl_write_full(property, value, NULL);
 }
 
-int sysctl_write_ip_neighbor_property(int af, const char *ifname, const char *property, const char *value);
-static inline int sysctl_write_ip_neighbor_property_uint32(int af, const char *ifname, const char *property, uint32_t value) {
+int sysctl_read_ip_property(int af, const char *ifname, const char *property, char **ret);
+int sysctl_write_ip_property(int af, const char *ifname, const char *property, const char *value, Hashmap **shadow);
+static inline int sysctl_write_ip_property_boolean(int af, const char *ifname, const char *property, bool value, Hashmap **shadow) {
+        return sysctl_write_ip_property(af, ifname, property, one_zero(value), shadow);
+}
+
+int sysctl_write_ip_neighbor_property(int af, const char *ifname, const char *property, const char *value, Hashmap **shadow);
+static inline int sysctl_write_ip_neighbor_property_uint32(int af, const char *ifname, const char *property, uint32_t value, Hashmap **shadow) {
         char buf[DECIMAL_STR_MAX(uint32_t)];
         xsprintf(buf, "%u", value);
-        return sysctl_write_ip_neighbor_property(af, ifname, property, buf);
+        return sysctl_write_ip_neighbor_property(af, ifname, property, buf, shadow);
 }
 
 #define DEFINE_SYSCTL_WRITE_IP_PROPERTY(name, type, format)           \
-        static inline int sysctl_write_ip_property_##name(int af, const char *ifname, const char *property, type value) { \
+        static inline int sysctl_write_ip_property_##name(int af, const char *ifname, const char *property, type value, Hashmap **shadow) { \
                 char buf[DECIMAL_STR_MAX(type)];                        \
                 xsprintf(buf, format, value);                           \
-                return sysctl_write_ip_property(af, ifname, property, buf); \
+                return sysctl_write_ip_property(af, ifname, property, buf, shadow); \
         }
 
 DEFINE_SYSCTL_WRITE_IP_PROPERTY(int, int, "%i");