学步园

IP_RECVDSTADDR undefined

刺猬@http://blog.csdn.net/littlehedgehog

今天写一个unp上面的例子程序，被IP_RECVDSTADDR undefined难倒了，gcc老是报错说该宏未定义，最后还是在老外的一个“开源苹果”网站查到原来linux修改了相关的函数定义，包括cmsghdr及setsockopt都采用了linux系统自己的定义。顺便说一下，这个貌似并不是linux故意另辟蹊径，在solari和bsd上面也是各不相同的。这里把代码贴出来，方便后面的同学。

#include "./unix.h"<br /> #include <sys/param.h></p> <p>ssize_t recvmsg_flags(int sockfd, void *buff, size_t nbytes, int *pflags, struct sockaddr *praddr, socklen_t *psocklen, struct in_addr *plocaladdr)<br /> {<br /> ssize_t ret;<br /> struct msghdr msg;<br /> struct cmsghdr *cmsgptr;<br /> struct iovec iov[1];<br /> union{<br /> struct cmsghdr cmsg;<br /> char control[CMSG_SPACE(sizeof(struct in_pktinfo))];<br /> }cmsg_un;<br /> msg.msg_name = praddr;<br /> msg.msg_namelen = *psocklen;<br /> iov[0].iov_base = buff;<br /> iov[0].iov_len = nbytes;<br /> msg.msg_iov = iov;<br /> msg.msg_iovlen = 1;<br /> msg.msg_control = cmsg_un.control;<br /> msg.msg_controllen = sizeof(cmsg_un.control);<br /> msg.msg_flags = 0; /*这个flags设置问题*/</p> <p> if ((ret = recvmsg(sockfd, &msg, 0)) < 0)<br /> {<br /> perror("recvmsg");<br /> return ret;<br /> }</p> <p> *psocklen = msg.msg_namelen;<br /> *pflags = msg.msg_flags;<br /> if ((msg.msg_controllen < sizeof(struct cmsghdr)) || (msg.msg_flags & MSG_CTRUNC) || !plocaladdr)<br /> {<br /> return ret;<br /> }<br /> for (cmsgptr = CMSG_FIRSTHDR(&msg); cmsgptr; cmsgptr = CMSG_NXTHDR(&msg, cmsgptr))<br /> {<br /> #if defined(IP_RECVDSTADDR)<br /> if (cmsgptr->cmsg_level == IPPROTO_IP && cmsgptr->cmsg_type == IP_RECVDSTADDR)<br /> {<br /> memcpy(plocaladdr, CMSG_DATA(cmsgptr), sizeof(struct in_addr));<br /> }<br /> #elif defined(IP_PKTINFO)<br /> if (cmsgptr->cmsg_level == SOL_IP && cmsgptr->cmsg_type == IP_PKTINFO)<br /> {<br /> struct in_pktinfo *in = (struct in_pktinfo *)CMSG_DATA(cmsgptr);<br /> memcpy(plocaladdr, &(in->ipi_addr), sizeof(struct in_addr));<br /> }<br /> #endif<br /> }<br /> return ret;</p> <p>}<br /> void echo(int sockfd, const struct sockaddr *pservaddr, socklen_t len, struct FILE *fp)<br /> {<br /> int ret;<br /> int flags = 0;<br /> const int on = 1;<br /> struct in_addr localaddr;<br /> char sendline[MAXLINE], recvline[MAXLINE];<br /> #if defined(IP_RECVDSTADDR)<br /> if (setsockopt(sockfd, IPPROTO_IP, IP_RECVDSTADDR, &on, sizeof(int)) < 0)<br /> {<br /> perror("setsockopt");<br /> return;<br /> }<br /> #elif defined(IP_PKTINFO)<br /> if (setsockopt(sockfd, IPPROTO_IP, IP_PKTINFO, &on, sizeof(int)) < 0)<br /> {<br /> perror("setsockopt");<br /> return;<br /> }<br /> #endif</p> <p> memset(&localaddr, 0x00, sizeof(struct in_addr));<br /> while (fgets(sendline, MAXLINE, fp) != NULL)<br /> {<br /> if (sendto(sockfd, sendline, strlen(sendline), 0x00, pservaddr, len) < 0)<br /> {<br /> perror("sendto");<br /> return;<br /> }<br /> if ((ret = recvmsg_flags(sockfd, recvline, MAXLINE, &flags, pservaddr, &len, &localaddr)) < 0)<br /> {<br /> return;<br /> }<br /> printf("recvmsg %d-byte datagram through %s/n", ret, inet_ntoa(localaddr));<br /> }<br /> }<br /> int main(int argc, char *argv[])<br /> {<br /> int connfd;<br /> struct sockaddr_in servaddr;<br /> if ((connfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)<br /> {<br /> perror("socket");<br /> exit(-1);<br /> }<br /> memset(&servaddr, 0x00, sizeof(servaddr));<br /> servaddr.sin_family = AF_INET;<br /> servaddr.sin_port = htons(1988);<br /> servaddr.sin_addr.s_addr = inet_addr("192.168.149.95");</p> <p> echo(connfd, (struct sockaddr *)&servaddr, sizeof(struct sockaddr_in), stdin);<br /> close(connfd);<br /> return 0;<br /> }