Add ioctl(SIOCGIFxxx) support (#197)

- SIOCGIFCONFIG: reads and enumerate all the network interfaces
- SIOCGIFADDR: reads network address for a given interface
- SIOCGIFFLAGS: reads network flags for a given interface
- SIOCGIFNETMASK: reads network netmask for a given interface
- SIOCGIFBRDADDR: reads network broadcast address for a given interface
- SIOCGIFDSTADDR: reads peer destination address for a given
  interface (not supported for Windows)

This change defines Linux ABI structs for the above interfaces and adds
polyfills to ensure they behave consistently on XNU and Windows.

libc/sock/internal.h

@@ -53,6 +53,45 @@ struct sockaddr_un_bsd {
   char sun_path[108];
 };
 
+/* -----------------------------------------------------------------------------------
+ * ioctl SIOCGIFCONF & others:
+ *
+ * BSD has a different structure. All the ioctl will adjust to use
+ * the ifreq with the ifreq_bsd
+ */
+struct ifreq_bsd {
+  union {
+    char ifrn_name[IFNAMSIZ];
+  } ifr_ifrn;
+
+  union {
+    /* Right now we only list the structures used by the few ioctl that are
+     * supported by Cosmopolitan. Add your own definition here if you need
+     * a particular ioctl that requires polyfill for BSD
+     */
+    struct  sockaddr_bsd ifru_addr;
+    struct  sockaddr_bsd ifru_netmask;
+    struct  sockaddr_bsd ifru_dstaddr;
+    struct  sockaddr_bsd ifru_broadaddr;
+    short   ifru_flags;
+    char    ifru_pad[16];   /* used as padding */
+  } ifr_ifru;
+};
+
+#pragma pack(4)
+struct ifconf_bsd {
+  uint32_t ifc_len;            /* size of buffer   */
+  union {
+    char *ifcu_buf;
+    struct ifreq_bsd *ifcu_req;
+  } ifc_ifcu;
+};
+#pragma pack()
+
+
+/* ------------------------------------------------------------------------------------*/
+
+
 struct SockFd {
   int family;
   int type;

libc/sock/sock.h

@@ -85,6 +85,59 @@ struct msghdr {            /* Linux+NT ABI */
   uint32_t msg_flags;      /* MSG_XXX */
 };
 
+
+/*
+ *  Structure used in SIOCGIFCONF request.
+ *  Used to retrieve interface configuration
+ *  for machine (useful for programs which
+ *  must know all networks accessible).
+ */
+struct ifconf {
+  uint64_t ifc_len;            /* size of buffer   */
+  union {
+    char *ifcu_buf;
+    struct ifreq *ifcu_req;
+  } ifc_ifcu;
+};
+
+
+/* Shortcuts to the ifconf buffer or ifreq array */
+#define ifc_buf ifc_ifcu.ifcu_buf       /* buffer address   */
+#define ifc_req ifc_ifcu.ifcu_req       /* array of structures  */
+
+#define IFHWADDRLEN	6
+#define IF_NAMESIZE	16
+#define IFNAMSIZ	IF_NAMESIZE
+struct ifreq {
+  union {
+    char ifrn_name[IFNAMSIZ];	/* Interface name, e.g. "en0".  */
+  } ifr_ifrn;
+
+  union {
+    struct sockaddr ifru_addr;          /* SIOCGIFADDR */
+    struct sockaddr ifru_dstaddr;       /* SIOCGIFDSTADDR */
+    struct sockaddr ifru_netmask;       /* SIOCGIFNETMASK */
+    struct sockaddr ifru_broadaddr;     /* SIOCGIFBRDADDR */
+    short           ifru_flags;         /* SIOCGIFFLAGS */
+    char            ifru_pad[24];   /* ifru_map is the largest, just pad */
+  } ifr_ifru;
+};
+
+#define ifr_name	ifr_ifrn.ifrn_name	/* interface name 	*/
+#define ifr_addr	ifr_ifru.ifru_addr	/* address		*/
+#define ifr_netmask	ifr_ifru.ifru_netmask	/* netmask		*/
+#define ifr_broadaddr	ifr_ifru.ifru_broadaddr	/* broadcast address	*/
+#define ifr_dstaddr	ifr_ifru.ifru_dstaddr	/* destination address	*/
+#define ifr_flags	ifr_ifru.ifru_flags	/* flags		*/
+
+#define _IOT_ifreq	_IOT(_IOTS(char),IFNAMSIZ,_IOTS(char),16,0,0)
+#define _IOT_ifreq_short _IOT(_IOTS(char),IFNAMSIZ,_IOTS(short),1,0,0)
+#define _IOT_ifreq_int	_IOT(_IOTS(char),IFNAMSIZ,_IOTS(int),1,0,0)
+
+#define IFF_UP  (1<<0)
+
+
+
 const char *inet_ntop(int, const void *, char *, uint32_t);
 int inet_aton(const char *, struct in_addr *);
 int inet_pton(int, const char *, void *);

libc/sock/sock.mk

@@ -33,6 +33,7 @@ LIBC_SOCK_A_DIRECTDEPS =			\
 	LIBC_NT_MSWSOCK				\
 	LIBC_NT_NTDLL				\
 	LIBC_NT_WS2_32				\
+	LIBC_NT_IPHLPAPI			\
 	LIBC_RUNTIME				\
 	LIBC_STDIO				\
 	LIBC_STR				\

libc/sock/socket-nt.c

@@ -19,12 +19,19 @@
 #include "libc/calls/internal.h"
 #include "libc/mem/mem.h"
 #include "libc/nt/winsock.h"
+#include "libc/nt/iphlpapi.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/yoink.inc"
 #include "libc/sysv/consts/fio.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/consts/sock.h"
 
+/* ioctl(SIOCGIFCONFIG) for Windows need to access the following functions through 
+ * weak reference. This ensure those symbols are not stripped during final link
+ */
+STATIC_YOINK("GetAdaptersAddresses");
+STATIC_YOINK("tprecode16to8");
+
 textwindows int sys_socket_nt(int family, int type, int protocol) {
   int64_t h;
   struct SockFd *sockfd;
@@ -42,6 +49,7 @@ textwindows int sys_socket_nt(int family, int type, int protocol) {
         return __winsockerr();
       }
     }
+
     sockfd = calloc(1, sizeof(struct SockFd));
     sockfd->family = family;
     sockfd->type = truetype;

libc/sock/socketpair-nt.c

@@ -27,7 +27,6 @@
 #include "libc/sysv/consts/sock.h"
 #include "libc/sysv/errfuns.h"
 
-// {{{ sys_socketpair_nt
 textwindows int sys_socketpair_nt(int family, int type, int proto, int sv[2]) {
   int64_t hpipe, h1, h2;
   int reader, writer, oflags;
@@ -89,4 +88,3 @@ textwindows int sys_socketpair_nt(int family, int type, int proto, int sv[2]) {
   sv[1] = writer;
   return 0;
 }
-// }}}