Implement part of Berkeley Socket API for libc-wasi (#1036)

Refer to [Networking API design](https://github.com/WebAssembly/WASI/issues/370)
and [feat(socket): berkeley socket API v2](https://github.com/WebAssembly/WASI/pull/459):

- Support the socket API of synchronous mode, including `socket/bind/listen/accept/send/recv/close/shutdown`,
    the asynchronous mode isn't supported yet.
- Support adding `--addr-pool=<pool1,pool2,..>` argument for command line to identify the valid ip address range
- Add socket-api sample and update the document

core/iwasm/libraries/lib-socket/src/wasi/wasi_socket_ext.c

@@ -0,0 +1,180 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <netinet/in.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <wasi/api.h>
+#include <wasi_socket_ext.h>
+
+#define HANDLE_ERROR(error)              \
+    if (error != __WASI_ERRNO_SUCCESS) { \
+        errno = error;                   \
+        return -1;                       \
+    }
+
+/* addr_num and port are in network order */
+static void
+ipv4_addr_to_wasi_addr(uint32_t addr_num, uint16_t port, __wasi_addr_t *out)
+{
+    out->kind = IPv4;
+    out->addr.ip4.port = ntohs(port);
+    out->addr.ip4.addr.n3 = (addr_num & 0xFF000000) >> 24;
+    out->addr.ip4.addr.n2 = (addr_num & 0x00FF0000) >> 16;
+    out->addr.ip4.addr.n1 = (addr_num & 0x0000FF00) >> 8;
+    out->addr.ip4.addr.n0 = (addr_num & 0x000000FF);
+}
+
+static __wasi_errno_t
+sockaddr_to_wasi_addr(const struct sockaddr *sock_addr, socklen_t addrlen,
+                      __wasi_addr_t *wasi_addr)
+{
+    __wasi_errno_t ret = __WASI_ERRNO_SUCCESS;
+    if (AF_INET == sock_addr->sa_family) {
+        assert(sizeof(struct sockaddr_in) == addrlen);
+
+        ipv4_addr_to_wasi_addr(
+            ((struct sockaddr_in *)sock_addr)->sin_addr.s_addr,
+            ((struct sockaddr_in *)sock_addr)->sin_port, wasi_addr);
+    }
+    else if (AF_INET6 == sock_addr->sa_family) {
+        // TODO: IPV6
+        ret = __WASI_ERRNO_AFNOSUPPORT;
+    }
+    else {
+        ret = __WASI_ERRNO_AFNOSUPPORT;
+    }
+
+    return ret;
+}
+
+static __wasi_errno_t
+sock_addr_remote(__wasi_fd_t fd, struct sockaddr *sock_addr, socklen_t *addrlen)
+{
+    __wasi_addr_t wasi_addr = { 0 };
+    __wasi_errno_t error;
+
+    error =
+        __wasi_sock_addr_remote(fd, (uint8_t *)&wasi_addr, sizeof(wasi_addr));
+    if (__WASI_ERRNO_SUCCESS != error) {
+        return error;
+    }
+
+    if (IPv4 == wasi_addr.kind) {
+        struct sockaddr_in sock_addr_in = { 0 };
+
+        sock_addr_in.sin_family = AF_INET;
+        sock_addr_in.sin_addr.s_addr = (wasi_addr.addr.ip4.addr.n3 << 24)
+                                       | (wasi_addr.addr.ip4.addr.n2 << 16)
+                                       | (wasi_addr.addr.ip4.addr.n1 << 8)
+                                       | wasi_addr.addr.ip4.addr.n0;
+        sock_addr_in.sin_port = htons(wasi_addr.addr.ip4.port);
+        memcpy(sock_addr, &sock_addr_in, sizeof(sock_addr_in));
+
+        *addrlen = sizeof(sock_addr_in);
+    }
+    else if (IPv6 == wasi_addr.kind) {
+        // TODO: IPV6
+        return __WASI_ERRNO_AFNOSUPPORT;
+    }
+    else {
+        return __WASI_ERRNO_AFNOSUPPORT;
+    }
+
+    return __WASI_ERRNO_SUCCESS;
+}
+
+int
+accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen)
+{
+    __wasi_addr_t wasi_addr = { 0 };
+    __wasi_fd_t new_sockfd;
+    __wasi_errno_t error;
+
+    error = __wasi_sock_accept(sockfd, &new_sockfd);
+    HANDLE_ERROR(error)
+
+    // error = sock_addr_remote(new_sockfd, addr, addrlen);
+    // HANDLE_ERROR(error)
+    *addrlen = 0;
+
+    return new_sockfd;
+}
+
+int
+bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen)
+{
+    __wasi_addr_t wasi_addr = { 0 };
+    __wasi_errno_t error;
+
+    error = sockaddr_to_wasi_addr(addr, addrlen, &wasi_addr);
+    HANDLE_ERROR(error)
+
+    error = __wasi_sock_bind(sockfd, &wasi_addr);
+    HANDLE_ERROR(error)
+
+    return __WASI_ERRNO_SUCCESS;
+}
+
+int
+connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen)
+{
+    __wasi_addr_t wasi_addr = { 0 };
+    __wasi_errno_t error;
+
+    error = sockaddr_to_wasi_addr(addr, addrlen, &wasi_addr);
+    HANDLE_ERROR(error)
+
+    error = __wasi_sock_connect(sockfd, &wasi_addr);
+    HANDLE_ERROR(error)
+
+    return __WASI_ERRNO_SUCCESS;
+}
+
+int
+listen(int sockfd, int backlog)
+{
+    __wasi_errno_t error = __wasi_sock_listen(sockfd, backlog);
+    HANDLE_ERROR(error)
+    return __WASI_ERRNO_SUCCESS;
+}
+
+int
+socket(int domain, int type, int protocol)
+{
+    // the stub of address pool fd
+    __wasi_fd_t poolfd = -1;
+    __wasi_fd_t sockfd;
+    __wasi_errno_t error;
+    __wasi_address_family_t af;
+    __wasi_sock_type_t socktype;
+
+    if (AF_INET == domain) {
+        af = INET4;
+    }
+    else if (AF_INET6 == domain) {
+        af = INET6;
+    }
+    else {
+        return __WASI_ERRNO_NOPROTOOPT;
+    }
+
+    if (SOCK_DGRAM == type) {
+        socktype = SOCKET_DGRAM;
+    }
+    else if (SOCK_STREAM == type) {
+        socktype = SOCKET_STREAM;
+    }
+    else {
+        return __WASI_ERRNO_NOPROTOOPT;
+    }
+
+    error = __wasi_sock_open(poolfd, af, socktype, &sockfd);
+    HANDLE_ERROR(error)
+
+    return sockfd;
+}