c - 解析并绑定(bind)到 IPv6 地址

Question

我编写了一个程序来解析地址或主机名，然后尝试以 listen(2) 模式绑定(bind)到该地址。由于某些奇怪的原因，我无法使用 IPv6 地址，程序在调用 bind(2) 后失败并显示“无效参数”。使用 IPv4，一切都像我期望的那样工作，名称得到解析，地址被简单地转换为二进制格式。

来源

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <netdb.h>
#include <unistd.h>

static int
resolve_addr (const char *hostname, const char *service, int family, struct addrinfo **result)
{
    struct addrinfo addr_hint;

    memset (&addr_hint, 0, sizeof (struct addrinfo));

    addr_hint.ai_socktype = SOCK_STREAM;
    addr_hint.ai_flags = AI_PASSIVE | AI_NUMERICSERV | AI_ADDRCONFIG;
    addr_hint.ai_family = family;

    return getaddrinfo (hostname, service, &addr_hint, result);
}

int
main (int argc, char *argv[])
{
    struct addrinfo *addr;
    int rval, sock, opt_val;

    rval = resolve_addr (argv[1], argv[2], AF_UNSPEC, &addr);

    if ( rval != 0 ){
        fprintf (stderr, "%s\n", gai_strerror (rval));
        return 1;
    }

    sock = socket (addr->ai_family, addr->ai_socktype | SOCK_NONBLOCK, addr->ai_protocol);

    if ( sock == -1 ){
        fprintf (stderr, "error socket: %s\n", strerror (errno));
        return 1;
    }

    if ( setsockopt (sock, SOL_SOCKET, SO_REUSEADDR, &opt_val, sizeof (opt_val)) == -1 ){
        fprintf (stderr, "error setsockopt: %s\n", strerror (errno));
        return 1;
    }

    if ( bind (sock, (struct sockaddr*) addr->ai_addr, sizeof (struct sockaddr)) == -1 ){
        fprintf (stderr, "error bind: %s\n", strerror (errno));
        return 1;
    }

    if ( listen (sock, 32) == -1 ){
        fprintf (stderr, "error listen: %s\n", strerror (errno));
        return 1;
    }

    sleep (120);

    freeaddrinfo (addr);
    close (sock);

    return 0;
}

用法

1. ./test_bind localhost 8888 # 有效
2. ./test_bind 0.0.0.0 8888 # 有效
3. ./test_bind 127.0.0.1 8888 # 有效
4. ./test_bind::8888 # 不起作用:参数无效
5. ./test_bind::1 8888 # 不起作用:参数无效

旁注

我使用 netcat 来查明我的系统是否有问题，但以下命令有效:

ncat -l::8888

在netstat中可以看到:

tcp6 0 0:::8888:::* LISTEN

Answer 1

我更新了我的代码，IPv4 和 IPv6 都已解析并成功绑定(bind)。问题出在 bind(2) 函数的第三个参数中，该函数正在根据结构计算地址的大小大小，而不是使用 getaddrinfo 结果中的值。

我替换了行:

if ( bind (sock, (struct sockaddr*) addr->ai_addr, sizeof (struct sockaddr)) == -1 ){

与:

if ( bind (sock, (struct sockaddr*) addr->ai_addr, addr->ai_addrlen) == -1 ){

完整来源

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
#include <unistd.h>

static int
resolve_addr (const char *hostname, const char *service, int family, struct addrinfo **result)
{
    struct addrinfo addr_hint;

    memset (&addr_hint, 0, sizeof (struct addrinfo));

    addr_hint.ai_socktype = SOCK_STREAM;
    addr_hint.ai_flags = AI_PASSIVE | AI_NUMERICSERV | AI_ADDRCONFIG;
    addr_hint.ai_family = family;

    return getaddrinfo (hostname, service, &addr_hint, result);
}


int
main (int argc, char *argv[])
{
    struct addrinfo *addr;
    int rval, sock, opt_val;

    rval = resolve_addr (argv[1], argv[2], AF_UNSPEC, &addr);

    if ( rval != 0 ){
        fprintf (stderr, "%s\n", gai_strerror (rval));
        return 1;
    }

    sock = socket (addr->ai_family, addr->ai_socktype | SOCK_NONBLOCK, addr->ai_protocol);

    if ( sock == -1 ){
        fprintf (stderr, "error socket: %s\n", strerror (errno));
        return 1;
    }

    opt_val = 1;

    if ( setsockopt (sock, SOL_SOCKET, SO_REUSEADDR, &opt_val, sizeof (opt_val)) == -1 ){
        fprintf (stderr, "error setsockopt: %s\n", strerror (errno));
        return 1;
    }

    if ( bind (sock, (struct sockaddr*) addr->ai_addr, addr->ai_addrlen) == -1 ){
        fprintf (stderr, "error bind: %s\n", strerror (errno));
        return 1;
    }

    if ( listen (sock, 32) == -1 ){
        fprintf (stderr, "error listen: %s\n", strerror (errno));
        return 1;
    }

    sleep (120);

    freeaddrinfo (addr);
    close (sock);

    return 0;
}