basic: introduce socket_protocol_{from,to}_name()

And use them where they can be applicable.

src/basic/generate-socket-protocol-list.sh

@@ -0,0 +1,5 @@
+#!/bin/sh -eu
+
+$1 -dM -include netinet/in.h - </dev/null | \
+        awk '/^#define[ \t]+IPPROTO_[^ \t]+[ \t]+[^ \t]/ { print $2; }' | \
+        sed -e 's/IPPROTO_//'

src/basic/meson.build

@@ -176,6 +176,8 @@ basic_sources_plain = files('''
         smack-util.c
         smack-util.h
         socket-label.c
+        socket-protocol-list.c
+        socket-protocol-list.h
         socket-util.c
         socket-util.h
         sparse-endian.h
@@ -255,11 +257,19 @@ errno_list_txt = custom_target(
         command : [generate_errno_list, cpp],
         capture : true)
 
+generate_socket_protocol_list = find_program('generate-socket-protocol-list.sh')
+socket_protocol_list_txt = custom_target(
+        'socket-protocol-list.txt',
+        output : 'socket-protocol-list.txt',
+        command : [generate_socket_protocol_list, cpp],
+        capture : true)
+
 generated_gperf_headers = []
 foreach item : [['af',     af_list_txt,     'af',         ''],
                 ['arphrd', arphrd_list_txt, 'arphrd',     'ARPHRD_'],
                 ['cap',    cap_list_txt,    'capability', ''],
-                ['errno',  errno_list_txt,  'errno',      '']]
+                ['errno',  errno_list_txt,  'errno',      ''],
+                ['socket-protocol', socket_protocol_list_txt, 'socket_protocol',     'IPPROTO_']]
 
         fname = '@0@-from-name.gperf'.format(item[0])
         gperf_file = custom_target(

src/basic/socket-protocol-list.c

@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <netinet/in.h>
+#include <string.h>
+
+#include "socket-protocol-list.h"
+#include "macro.h"
+
+static const struct socket_protocol_name* lookup_socket_protocol(register const char *str, register GPERF_LEN_TYPE len);
+
+#include "socket-protocol-from-name.h"
+#include "socket-protocol-to-name.h"
+
+const char *socket_protocol_to_name(int id) {
+
+        if (id < 0)
+                return NULL;
+
+        if (id >= (int) ELEMENTSOF(socket_protocol_names))
+                return NULL;
+
+        return socket_protocol_names[id];
+}
+
+int socket_protocol_from_name(const char *name) {
+        const struct socket_protocol_name *sc;
+
+        assert(name);
+
+        sc = lookup_socket_protocol(name, strlen(name));
+        if (!sc)
+                return 0;
+
+        return sc->id;
+}
+
+int socket_protocol_max(void) {
+        return ELEMENTSOF(socket_protocol_names);
+}

src/basic/socket-protocol-list.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+const char *socket_protocol_to_name(int id);
+int socket_protocol_from_name(const char *name);
+
+int socket_protocol_max(void);

src/basic/socket-protocol-to-name.awk

@@ -0,0 +1,9 @@
+BEGIN{
+        print "static const char* const socket_protocol_names[] = { "
+}
+!/HOPOPTS/ {
+        printf "        [IPPROTO_%s] = \"%s\",\n", $1, tolower($1)
+}
+END{
+        print "};"
+}