json-util: generalize json_dispatch_ifindex()

Let's move the helper from nss-resolve.c to generic code, as it's going
to be useful in #34640.

Also, let's tighten the rules, and refuse negative ifindexes, because
they are invalid.

3 files changed, 21 insertions, 17 deletions

diff --git a/src/libsystemd/sd-json/json-util.c b/src/libsystemd/sd-json/json-util.c
index a1b2ebc0fe..db7a2ac1e8 100644
--- a/src/libsystemd/sd-json/json-util.c
+++ b/src/libsystemd/sd-json/json-util.c
@@ -306,6 +306,26 @@ int json_dispatch_pidref(const char *name, sd_json_variant *variant, sd_json_dis
         return 0;
 }
 
+int json_dispatch_ifindex(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
+        int *ifi = ASSERT_PTR(userdata), r, t;
+
+        if (sd_json_variant_is_null(variant)) {
+                *ifi = 0;
+                return 0;
+        }
+
+        r = sd_json_dispatch_int(name, variant, flags, &t);
+        if (r < 0)
+                return r;
+
+        /* If SD_JSON_RELAX is set allow a zero interface index, otherwise refuse. */
+        if (t < (FLAGS_SET(flags, SD_JSON_RELAX) ? 0 : 1))
+                return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is out of bounds for an interface index.", strna(name));
+
+        *ifi = t;
+        return 0;
+}
+
 int json_variant_new_devnum(sd_json_variant **ret, dev_t devnum) {
         if (devnum == 0)
                 return sd_json_variant_new_null(ret);
diff --git a/src/libsystemd/sd-json/json-util.h b/src/libsystemd/sd-json/json-util.h
index 81c0fd02a6..b824fa8a81 100644
--- a/src/libsystemd/sd-json/json-util.h
+++ b/src/libsystemd/sd-json/json-util.h
@@ -115,6 +115,7 @@ int json_dispatch_in_addr(const char *name, sd_json_variant *variant, sd_json_di
 int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_pidref(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_devnum(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
+int json_dispatch_ifindex(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 
 static inline int json_variant_unbase64_iovec(sd_json_variant *v, struct iovec *ret) {
         return sd_json_variant_unbase64(v, ret ? &ret->iov_base : NULL, ret ? &ret->iov_len : NULL);
diff --git a/src/nss-resolve/nss-resolve.c b/src/nss-resolve/nss-resolve.c
index 91c5f11cb2..1c64ac2fd0 100644
--- a/src/nss-resolve/nss-resolve.c
+++ b/src/nss-resolve/nss-resolve.c
@@ -96,23 +96,6 @@ static uint32_t ifindex_to_scopeid(int family, const void *a, int ifindex) {
         return in6_addr_is_link_local(&in6) ? ifindex : 0;
 }
 
-static int json_dispatch_ifindex(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
-        int *ifi = ASSERT_PTR(userdata);
-        int64_t t;
-
-        assert(variant);
-
-        if (!sd_json_variant_is_integer(variant))
-                return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not an integer.", strna(name));
-
-        t = sd_json_variant_integer(variant);
-        if (t > INT_MAX)
-                return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is out of bounds for an interface index.", strna(name));
-
-        *ifi = (int) t;
-        return 0;
-}
-
 static int json_dispatch_family(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
         int *family = ASSERT_PTR(userdata);
         int64_t t;