conf-parser: move config_parse_ip_protocol() from network/netdev/fou-tunnel.c

The function is generic enough. Currently it is used at only one place.
But it will be used at another place.

src/shared/conf-parser.c

@@ -24,6 +24,7 @@
 #include "hostname-util.h"
 #include "id128-util.h"
 #include "in-addr-util.h"
+#include "ip-protocol-list.h"
 #include "log.h"
 #include "macro.h"
 #include "missing_network.h"
@@ -2082,3 +2083,39 @@ int config_parse_timezone(
 
         return free_and_strdup_warn(tz, rvalue);
 }
+
+int config_parse_ip_protocol(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        uint8_t *proto = ASSERT_PTR(data);
+        int r;
+
+        r = isempty(rvalue) ? 0 : parse_ip_protocol_full(rvalue, /* relaxed= */ ltype);
+        if (r < 0) {
+                log_syntax(unit, LOG_WARNING, filename, line, r,
+                           "Failed to parse '%s=%s', ignoring: %m",
+                           lvalue, rvalue);
+                return 0;
+        }
+
+        if (r > UINT8_MAX) {
+                /* linux/fib_rules.h and linux/fou.h define the netlink field as one byte, so we need to
+                 * reject protocols numbers that don't fit in one byte. */
+                log_syntax(unit, LOG_WARNING, filename, line, r,
+                           "Invalid '%s=%s', allowed range is 0..255, ignoring.",
+                           lvalue, rvalue);
+                return 0;
+        }
+
+        *proto = r;
+        return 1; /* done. */
+}

src/shared/conf-parser.h

@@ -290,6 +290,7 @@ CONFIG_PARSER_PROTOTYPE(config_parse_pid);
 CONFIG_PARSER_PROTOTYPE(config_parse_sec_fix_0);
 CONFIG_PARSER_PROTOTYPE(config_parse_timezone);
 CONFIG_PARSER_PROTOTYPE(config_parse_calendar);
+CONFIG_PARSER_PROTOTYPE(config_parse_ip_protocol);
 
 typedef enum Disabled {
         DISABLED_CONFIGURATION,