用户层通过socket使用XFRM_MSG_GETSA获取xfrm_algo_auth信息的C代码示例

以下是一个使用socket获取xfrm_algo_auth信息的C代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <linux/xfrm.h>

#define BUF_SIZE 4096

int main(int argc, char *argv[]) {
    int sockfd, ret;
    char buf[BUF_SIZE];
    struct msghdr msg;
    struct iovec iov;
    struct sockaddr_nl nladdr;
    struct nlmsghdr *nlhdr;
    struct xfrm_userpolicy_info up_info;
    struct xfrm_usersa_info sa_info;
    struct xfrm_algo_auth *auth;
    int nlgroups = XFRMNLGRP_NONE;

    sockfd = socket(AF_NETLINK, SOCK_RAW, NETLINK_XFRM);
    if (sockfd < 0) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    memset(&nladdr, 0, sizeof(nladdr));
    nladdr.nl_family = AF_NETLINK;

    ret = bind(sockfd, (struct sockaddr *)&nladdr, sizeof(nladdr));
    if (ret < 0) {
        perror("bind");
        exit(EXIT_FAILURE);
    }

    memset(&up_info, 0, sizeof(up_info));
    up_info.sel.family = AF_INET;
    up_info.sel.saddr.a4 = inet_addr("192.168.1.1");
    up_info.sel.prefixlen_d = 32;
    up_info.dir = XFRM_POLICY_OUT;

    memset(&sa_info, 0, sizeof(sa_info));
    sa_info.sel.family = AF_INET;
    sa_info.sel.saddr.a4 = inet_addr("192.168.1.1");
    sa_info.sel.prefixlen_d = 32;
    sa_info.mode = XFRM_MODE_TUNNEL;
    sa_info.reqid = 1;

    memset(&msg, 0, sizeof(msg));
    nlhdr = (struct nlmsghdr *)buf;
    nlhdr->nlmsg_len = NLMSG_LENGTH(sizeof(up_info));
    nlhdr->nlmsg_type = XFRM_MSG_NEWPOLICY;
    nlhdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL;
    nlhdr->nlmsg_seq = 1;
    nlhdr->nlmsg_pid = getpid();
    memcpy(NLMSG_DATA(nlhdr), &up_info, sizeof(up_info));
    iov.iov_base = (void *)nlhdr;
    iov.iov_len = nlhdr->nlmsg_len;
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;

    ret = sendmsg(sockfd, &msg, 0);
    if (ret < 0) {
        perror("sendmsg");
        exit(EXIT_FAILURE);
    }

    memset(&msg, 0, sizeof(msg));
    nlhdr = (struct nlmsghdr *)buf;
    nlhdr->nlmsg_len = NLMSG_LENGTH(sizeof(sa_info));
    nlhdr->nlmsg_type = XFRM_MSG_NEWSA;
    nlhdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL;
    nlhdr->nlmsg_seq = 2;
    nlhdr->nlmsg_pid = getpid();
    memcpy(NLMSG_DATA(nlhdr), &sa_info, sizeof(sa_info));
    iov.iov_base = (void *)nlhdr;
    iov.iov_len = nlhdr->nlmsg_len;
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;

    ret = sendmsg(sockfd, &msg, 0);
    if (ret < 0) {
        perror("sendmsg");
        exit(EXIT_FAILURE);
    }

    memset(&msg, 0, sizeof(msg));
    nlhdr = (struct nlmsghdr *)buf;
    nlhdr->nlmsg_len = NLMSG_LENGTH(sizeof(struct xfrm_usersa_id));
    nlhdr->nlmsg_type = XFRM_MSG_GETSA;
    nlhdr->nlmsg_flags = NLM_F_REQUEST;
    nlhdr->nlmsg_seq = 3;
    nlhdr->nlmsg_pid = getpid();
    struct xfrm_usersa_id *id = (struct xfrm_usersa_id *)NLMSG_DATA(nlhdr);
    id->daddr.a4 = inet_addr("192.168.1.1");
    id->spi = 1234;
    iov.iov_base = (void *)nlhdr;
    iov.iov_len = nlhdr->nlmsg_len;
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;

    ret = sendmsg(sockfd, &msg, 0);
    if (ret < 0) {
        perror("sendmsg");
        exit(EXIT_FAILURE);
    }

    memset(&msg, 0, sizeof(msg));
    iov.iov_base = buf;
    iov.iov_len = BUF_SIZE;
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;
    msg.msg_name = &nladdr;
    msg.msg_namelen = sizeof(nladdr);

    ret = recvmsg(sockfd, &msg, 0);
    if (ret < 0) {
        perror("recvmsg");
        exit(EXIT_FAILURE);
    }

    nlhdr = (struct nlmsghdr *)buf;
    while (NLMSG_OK(nlhdr, ret)) {
        if (nlhdr->nlmsg_type == XFRM_MSG_NEWSA) {
            struct xfrm_usersa_info *sa = (struct xfrm_usersa_info *)NLMSG_DATA(nlhdr);
            if (sa->id.daddr.a4 == inet_addr("192.168.1.1") && sa->id.spi == 1234) {
                auth = (struct xfrm_algo_auth *)((char *)sa + NLMSG_ALIGN(sa->hdr.len) + sizeof(struct xfrm_algo));
                printf("auth algo name: %s\n", auth->alg_name);
                printf("auth key length: %d\n", auth->alg_key_len);
                break;
            }
        }
        nlhdr = NLMSG_NEXT(nlhdr, ret);
    }

    memset(&msg, 0, sizeof(msg));
    nlhdr = (struct nlmsghdr *)buf;
    nlhdr->nlmsg_len = NLMSG_LENGTH(sizeof(up_info));
    nlhdr->nlmsg_type = XFRM_MSG_DELPOLICY;
    nlhdr->nlmsg_flags = NLM_F_REQUEST;
    nlhdr->nlmsg_seq = 4;
    nlhdr->nlmsg_pid = getpid();
    memcpy(NLMSG_DATA(nlhdr), &up_info, sizeof(up_info));
    iov.iov_base = (void *)nlhdr;
    iov.iov_len = nlhdr->nlmsg_len;
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;

    ret = sendmsg(sockfd, &msg, 0);
    if (ret < 0) {
        perror("sendmsg");
        exit(EXIT_FAILURE);
    }

    memset(&msg, 0, sizeof(msg));
    nlhdr = (struct nlmsghdr *)buf;
    nlhdr->nlmsg_len = NLMSG_LENGTH(sizeof(sa_info));
    nlhdr->nlmsg_type = XFRM_MSG_DELSA;
    nlhdr->nlmsg_flags = NLM_F_REQUEST;
    nlhdr->nlmsg_seq = 5;
    nlhdr->nlmsg_pid = getpid();
    memcpy(NLMSG_DATA(nlhdr), &sa_info, sizeof(sa_info));
    iov.iov_base = (void *)nlhdr;
    iov.iov_len = nlhdr->nlmsg_len;
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;

    ret = sendmsg(sockfd, &msg, 0);
    if (ret < 0) {
        perror("sendmsg");
        exit(EXIT_FAILURE);
    }

    close(sockfd);
    return 0;
}

该示例创建了一个xfrm policy和一个xfrm sa，并通过socket发送XFRM_MSG_GETSA消息获取xfrm sa的信息，包括xfrm_algo_auth的算法名称和密钥长度。最后删除创建的xfrm policy和xfrm sa