【Linux】linux c语言调用send()接口内核调用流程

1、C语言测试代码：

#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <err.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>#define BSIZE 0x1000/* "BSIZE" is the size of the buffer we use to read from the socket. */ int main ()
{struct addrinfo hints, *res;int socketfd;char *msg;int bytes;char buf[BSIZE+10];memset (&hints, 0, sizeof(hints)); hints.ai_family = PF_UNSPEC;hints.ai_socktype = SOCK_STREAM;//套接字流方式tcp/* Get one of the web pages here. //www.lemoda.net*/socketfd = getaddrinfo ("www.lemoda.net", "http", &hints, &res);//获取主机地址信息if (socketfd) {fprintf (stderr, "%s\n", gai_strerror(socketfd));exit (1);}//建立socketsocketfd = socket (AF_INET, SOCK_STREAM, 0);if (socketfd < 0) {fprintf (stderr, "socket: %s\n", strerror (errno));exit (1);}//链接socketif (connect(socketfd, res->ai_addr, res->ai_addrlen) < 0) {fprintf (stderr, "connect: %s\n", strerror (errno));close(socketfd);exit (1);}if (socketfd == -1) exit (1);/* "format" is the format of the HTTP request we send to the web server. */ const char * format =  "GET /%s HTTP/1.0\r\nHost: %s\r\nUser-Agent: fetch.c\r\n\r\n";asprintf (&msg, format, "momoe/", "www.lemoda.net");send (socketfd, msg, strlen (msg), 0);bytes = recvfrom (socketfd, buf, BSIZE, 0, 0, 0);if (bytes == -1) {fprintf (stderr, "%s\n", strerror(errno));exit (1);}buf[bytes] = '\0';printf ("Get data from remote: \n%s\n", buf);free (msg);        freeaddrinfo (res);return 0;
}

2、执行成功后内核打印日志：

完整日志：
p01-network/tcp/kern_2024_11_05_22_04_24_run_test.sh_a.out.log · r77683962/linux-6.9.0-testlog - Gitee.com

基于完整日志过滤" a.out "后的日志，因为第1步c代码编译出来的可执行文件叫a.out，执行时内核中的进程名是a.out

01-network/tcp/kern_2024_11_05_22_04_24_a.out_grep.log · r77683962/linux-6.9.0-testlog - Gitee.com

3、梳理出来的函数调用关系（从系统调用到驱动层）：

SYSCALL_DEFINE6(sendto
   __sys_sendto
       __sock_sendmsg
           sock_sendmsg_nosec
               netlink_sendmsg
                   netlink_alloc_large_skb
                   netlink_unicast
                       netlink_unicast_kernel
                           sock_put
                           netlink_deliver_tap_kernel
                               netlink_deliver_tap
                                   __netlink_deliver_tap
                                       __netlink_deliver_tap_skb
                                           dev_queue_xmit Y
                                               __dev_queue_xmit Y
                                                   __dev_xmit_skb
                                                       sch_direct_xmit
                                                           dev_hard_start_xmit Y
                                                   dev_hard_start_xmit
                                                       xmit_one Y
                                                           netdev_start_xmit
                                                               __netdev_start_xmit
                                                                   e1000_xmit_frame