LibC: Add definitions/stubs for IPv6 functionality

This lets us build some of the ports without patching out any of their
IPv6 stuff.

Userland/Libraries/LibC/CMakeLists.txt

@@ -18,6 +18,7 @@ set(LIBC_SOURCES
     malloc.cpp
     mman.cpp
     mntent.cpp
+    net.cpp
     netdb.cpp
     poll.cpp
     pthread_forward.cpp

Userland/Libraries/LibC/net.cpp

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibC/errno.h>
+#include <LibC/net/if.h>
+#include <LibC/netinet/in.h>
+
+in6_addr in6addr_any = IN6ADDR_ANY_INIT;
+
+unsigned int if_nametoindex([[maybe_unused]] const char* ifname)
+{
+    errno = ENODEV;
+    return -1;
+}
+
+char* if_indextoname([[maybe_unused]] unsigned int ifindex, [[maybe_unused]] char* ifname)
+{
+    errno = ENXIO;
+    return nullptr;
+}

Userland/Libraries/LibC/net/if.h

@@ -46,4 +46,7 @@ struct ifreq {
 #define ifr_hwaddr ifr_ifru.ifru_hwaddr       // MAC address
 };
 
+unsigned int if_nametoindex(const char* ifname);
+char* if_indextoname(unsigned int ifindex, char* ifname);
+
 __END_DECLS

Userland/Libraries/LibC/netinet/in.h

@@ -25,6 +25,12 @@ in_addr_t inet_addr(const char*);
 #define IP_MULTICAST_LOOP 3
 #define IP_ADD_MEMBERSHIP 4
 #define IP_DROP_MEMBERSHIP 5
+#define IP_MULTICAST_IF 6
+#define IP_MULTICAST_TTL 7
+
+/* Make sure these don't overlap with any other IPv4 and IPv6 options */
+#define MCAST_JOIN_SOURCE_GROUP 100
+#define MCAST_LEAVE_SOURCE_GROUP 101
 
 #define IPPORT_RESERVED 1024
 #define IPPORT_USERRESERVED 5000
@@ -47,10 +53,39 @@ struct ip_mreq {
     struct in_addr imr_interface;
 };
 
+struct group_source_req {
+    uint32_t gsr_interface;
+    struct sockaddr_storage gsr_group;
+    struct sockaddr_storage gsr_source;
+};
+
+struct ip_mreq_source {
+    struct in_addr imr_multiaddr;
+    struct in_addr imr_sourceaddr;
+    struct in_addr imr_interface;
+};
+
+#define IPV6_UNICAST_HOPS 1
+#define IPV6_MULTICAST_HOPS 2
+#define IPV6_MULTICAST_LOOP 3
+#define IPV6_MULTICAST_IF 4
+#define IPV6_ADD_MEMBERSHIP 5
+#define IPV6_DROP_MEMBERSHIP 6
+#define IP_ADD_SOURCE_MEMBERSHIP 7
+#define IP_DROP_SOURCE_MEMBERSHIP 8
+#define IPV6_V6ONLY 9
+
 struct in6_addr {
     uint8_t s6_addr[16];
 };
 
+#define IN6ADDR_ANY_INIT                               \
+    {                                                  \
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 \
+    }
+
+extern struct in6_addr in6addr_any;
+
 struct sockaddr_in6 {
     sa_family_t sin6_family;   // AF_INET6.
     in_port_t sin6_port;       // Port number.
@@ -59,4 +94,9 @@ struct sockaddr_in6 {
     uint32_t sin6_scope_id;    // Set of interfaces for a scop
 };
 
+struct ipv6_mreq {
+    struct in6_addr ipv6mr_multiaddr;
+    uint32_t ipv6mr_interface;
+};
+
 __END_DECLS