feat: dns resolve of udp proxy's remote host

include/dns.h

@@ -0,0 +1,6 @@
+#ifndef _DNS_H_
+#define _DNS_H_
+
+char* dns_resolve(char *domain);
+
+#endif

include/network.h

@@ -3,6 +3,7 @@
 
 extern int proxy_exit;
 
+int is_ip_addr(char *address);
 int get_available_port(unsigned short range_start, unsigned short range_end);
 void proxy(char *server_ip, int server_port, char *listen_ip, int listen_port);
 

src/dns.c

@@ -0,0 +1,102 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <netdb.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include "dns.h"
+
+char** init_dns_result();
+void add_dns_result(char **dns_result, char *str);
+void free_dns_result(char **dns_result);
+char** ipv4_dns_resolve(char *domain);
+char** ipv6_dns_resolve(char *domain);
+
+char** init_dns_result() { // 初始化DNS解析存储结构
+    char **dns_result = (char**)malloc(sizeof(char*));
+    dns_result[0] = NULL;
+    return dns_result;
+}
+
+void add_dns_result(char **dns_result, char *str) { // 添加DNS解析记录
+    int num = 0;
+    while(dns_result[num++] != NULL); // 获取原存储个数
+    dns_result = (char**)realloc(dns_result, sizeof(char**) * (num + 1));
+    dns_result[num - 1] = strcpy((char*)malloc(strlen(str) + 1), str);
+    dns_result[num] = NULL; // 结束标志
+}
+
+void free_dns_result(char **dns_result) { // 释放DNS解析结果
+    int num = 0;
+    while(dns_result[num] != NULL) { // 逐个释放
+        free(dns_result[num++]);
+    }
+}
+
+char** ipv4_dns_resolve(char *domain) { // DNS解析IPv4地址
+    char **result = init_dns_result();
+    char ip_str[16]; // IPv4地址字符串 (3 * 4 + 1 * 3 + 1)
+    struct sockaddr_in *ipv4_addr;
+    struct addrinfo *answer, hint, *p;
+    bzero(&hint, sizeof(hint)); // 清空为0x00
+    hint.ai_family = AF_INET;
+    hint.ai_socktype = SOCK_STREAM;
+    int ret = getaddrinfo(domain, NULL, &hint, &answer); // 发起解析
+    if (ret != 0) { // 解析失败
+        printf("[Shadowsocks Bootstrap] IPv4 DNS resolve `%s`: %s\n", domain, gai_strerror(ret));
+        return result; // 返回空数据
+    }
+    for (p = answer; p != NULL; p = p->ai_next) { // 遍历解析结果
+        ipv4_addr = (struct sockaddr_in*)(p->ai_addr); // 获取IPv4地址
+        inet_ntop(AF_INET, &ipv4_addr->sin_addr, ip_str, sizeof(ip_str)); // 转化为字符串形式
+        add_dns_result(result, ip_str);
+    }
+    freeaddrinfo(answer); // 释放解析结果
+    return result;
+}
+
+char** ipv6_dns_resolve(char *domain) { // DNS解析IPv6地址
+    char **result = init_dns_result();
+    char ip_str[40]; // IPv6地址字符串 (4 * 8 + 1 * 7 + 1)
+    struct sockaddr_in6 *ipv6_addr;
+    struct addrinfo *answer, hint, *p;
+    bzero(&hint, sizeof(hint)); // 清空为0x00
+    hint.ai_family = AF_INET6;
+    hint.ai_socktype = SOCK_STREAM;
+    int ret = getaddrinfo(domain, NULL, &hint, &answer); // 发起解析
+    if (ret != 0) { // 解析失败
+        printf("[Shadowsocks Bootstrap] IPv6 DNS resolve `%s`: %s\n", domain, gai_strerror(ret));
+        return result; // 返回空数据
+    }
+    for (p = answer; p != NULL; p = p->ai_next) { // 遍历解析结果
+        ipv6_addr = (struct sockaddr_in6*)(p->ai_addr); // 获取IPv6地址
+        inet_ntop(AF_INET6, &ipv6_addr->sin6_addr, ip_str, sizeof(ip_str)); // 转化为字符串形式
+        add_dns_result(result, ip_str);
+    }
+    freeaddrinfo(answer); // 释放解析结果
+    return result;
+}
+
+char* dns_resolve(char *domain) { // DNS解析 返回首个IP地址 IPv4优先
+    int num = 0;
+    char **result = init_dns_result();
+    result = ipv4_dns_resolve(domain); // IPv4解析
+    while(result[num++] != NULL); // num - 1 为IPv4地址数
+    if (num - 1 != 0) { // 存在IPv4解析
+        char *tmp = strcpy((char*)malloc(strlen(result[0]) + 1), result[0]);
+        free_dns_result(result); // 释放IPv4结果
+        return tmp; // 返回首个IPv4地址
+    }
+    free_dns_result(result); // 释放IPv4结果
+    result = ipv6_dns_resolve(domain);
+    num = 0;
+    while(result[num++] != NULL); // num - 1 为IPv6地址数
+    if (num - 1 == 0) { // 无IPv6解析
+        free_dns_result(result); // 释放IPv6结果
+        return NULL;
+    }
+    char *tmp = strcpy((char*)malloc(strlen(result[0]) + 1), result[0]);
+    free_dns_result(result); // 释放IPv6结果
+    return tmp; // 返回首个IPv6地址
+}

src/network.c

@@ -13,6 +13,20 @@
 
 int proxy_exit;
 
+int get_random_num(int range_start, int range_end);
+int check_port_available(unsigned int port, int is_udp, int is_ipv6);
+int is_ipv4_addr(char *address);
+int is_ipv6_addr(char *address);
+int create_ipv4_udp_sock(char *address, int port);
+int create_ipv6_udp_sock(char *address, int port);
+long ipv4_receive(int fd, char *buffer, int buffer_size, int timeout, struct sockaddr_in sa);
+long ipv6_receive(int fd, char *buffer, int buffer_size, int timeout, struct sockaddr_in6 sa);
+long ipv4_send_and_receive(char *ipv4_server_ip, int ipv4_server_port, char *send_buffer, long send_len, char *recv_buffer);
+long ipv6_send_and_receive(char *ipv6_server_ip, int ipv6_server_port, char *send_buffer, long send_len, char *recv_buffer);
+long send_and_receive(char *server_ip, int server_port, char *send_buffer, long send_len, char *recv_buffer);
+void ipv4_proxy(void *ipv4_info);
+void ipv6_proxy(void *ipv6_info);
+
 typedef struct ipv4_proxy_info {
     char *server_ip;
     int server_port;
@@ -105,9 +119,23 @@ int get_available_port(unsigned short range_start, unsigned short range_end) { /
     }
 }
 
+int is_ipv4_addr(char *address) { // 判断是否为IPv4地址
+    if (inet_addr(address) == -1) {
+        return 0;
+    }
+    return 1;
+}
+
 int is_ipv6_addr(char *address) { // 判断是否为IPv6地址
-    struct sockaddr_in6 temp;
-    if (!inet_aton(address, (struct in_addr*)&temp.sin6_addr)) { // IPv6 address
+    char buf[sizeof(struct in6_addr)];
+    if (inet_pton(AF_INET6, address, buf) <= 0) {
+        return 0;
+    }
+    return 1;
+}
+
+int is_ip_addr(char *address) { // 判断是否为IP地址
+    if (is_ipv4_addr(address) || is_ipv6_addr(address)) {
         return 1;
     }
     return 0;
@@ -228,7 +256,7 @@ void ipv4_proxy(void *ipv4_info) { // 代理IPv4客户端
     char *recv_buffer = (char*)malloc(BUFFER_SIZE); // 申请接收缓冲区内存
     long recv_len = send_and_receive(info->server_ip, info->server_port, info->buffer, info->len, recv_buffer); // 服务端交互
     if (recv_len < 0) { // 服务端超时
-        printf("[Shadowsocks Bootstrap] Server return timeout\n");
+        printf("[Shadowsocks Bootstrap] UDP Proxy: server return timeout\n");
     } else {
         if (sendto(info->ipv4_client_fd, recv_buffer, recv_len, 0, (struct sockaddr*)&(info->ipv4_client_addr), sizeof(info->ipv4_client_addr)) < 0) { // 服务端数据返回给客户端
             perror("[Shadowsocks Bootstrap] IPv4 UDP return failed");

src/process.c

@@ -6,6 +6,7 @@
 #include <sys/prctl.h>
 #include "network.h"
 #include "process.h"
+#include "dns.h"
 
 char **shadowsocks_args;
 char *plugin_file;
@@ -201,10 +202,26 @@ void start_bootstrap(char *ss_type) { // start shadowsocks and plugin (optional)
     process_exec(); // exec child process
     usleep(500 * 1000); // wait 500ms for plugin start
     if (plugin_file != NULL) { // start udp proxy when using plugin
-        if (!strcmp(ss_type, "sslocal")) { // local mode
-            proxy(SS_REMOTE_HOST, atoi(SS_REMOTE_PORT), SS_LOCAL_HOST, atoi(SS_LOCAL_PORT));
-        } else { // server mode
-            proxy(SS_LOCAL_HOST, atoi(SS_LOCAL_PORT), SS_REMOTE_HOST, atoi(SS_REMOTE_PORT));
+        char *remote_ip;
+        if (is_ip_addr(SS_REMOTE_HOST)) { // remote_host -> ip address
+            remote_ip = SS_REMOTE_HOST;
+        } else { // remote_host -> domain
+            printf("[Shadowsocks Bootstrap] DNS Resolve: %s\n", SS_REMOTE_HOST);
+            remote_ip = dns_resolve(SS_REMOTE_HOST); // dns resolve
+            if (remote_ip == NULL) { // no result
+                printf("[Shadowsocks Bootstrap] DNS record not found.\n");
+            } else { // dns resolve success
+                printf("[Shadowsocks Bootstrap] %s => %s\n", SS_REMOTE_HOST, remote_ip);
+            }
+        }
+        if (remote_ip == NULL) { // resolve error
+            printf("[Shadowsocks Bootstrap] Skip UDP Proxy.\n");
+        } else { // udp proxy
+            if (!strcmp(ss_type, "sslocal")) { // local mode
+                proxy(remote_ip, atoi(SS_REMOTE_PORT), SS_LOCAL_HOST, atoi(SS_LOCAL_PORT));
+            } else { // server mode
+                proxy(SS_LOCAL_HOST, atoi(SS_LOCAL_PORT), remote_ip, atoi(SS_REMOTE_PORT));
+            }
         }
     }
     g_main_loop_run(main_loop); // into main loop for wait