Question

我有项目代码，它创建一个UDP套接字来接收多播数据包。该代码可移植用于Linux和Solaris操作系统。我的项目的扩展是在使用recvmsg（）函数时检索UDP数据包的源IP地址。我曾就这个问题询问了一位专家，她提到Linux似乎能够提供源IP地址，但Solaris在使用recvmsg（）函数时可能没有。所以我在这里提出问题，我能在Solaris 10上使用recvmsg（）检索源IP地址吗？

操作系统：Solaris 10，Sunstudio 12 cc（无U1或U2）。代码库：C / C ++

//Socket initially opened with the following options from a different function.
// This connects the socket to receive multicast:
setsockopt(data->fd, IPPROTO_IP, IP_ADD_SOURCE_MEMBERSHIP,
    (char *)&mregs, sizeof(mregs) ) < 0)

//A different function performs an infinite loop reading from the socket:

struct iovec vector;
vector.iov_base = buf;     //passed in param
vector.iov_len = len;      //passed in param
struct msghdr msg;
char    caddr[100] ;
msg.msg_name =  caddr;
msg.msg_namelen = 100;
msg.msg_iov = &vector;
msg.msg_iovlen = 1;
int flags = 0;

char controlBuffer[1024];
msg.msg_control = controlBuffer;
msg.msg_controllen = 1024;

bytes = ::recvmsg(data->fd, &msg, flags);

//removed error checking    

struct cmsghdr *cmsg;
struct in_pktinfo *dest_ip_ptr;
rrcp_u32_t dest_ip = 0;
cmsg = CMSG_FIRSTHDR(&msg);
for ( cmsg = CMSG_FIRSTHDR(&msg);
    cmsg != NULL;
    cmsg = CMSG_NXTHDR( &msg, cmsg ) )
{
    //if ( cmsg->cmsg_type == IPPROTO_IP && cmsg->cmsg_level == IP_PKTINFO )
    {
#ifdef Linux
        struct in_pktinfo *dest_ip_ptr = (struct in_pktinfo*)CMSG_DATA(cmsg);
        dest_ip = dest_ip_ptr->ipi_addr.s_addr;
#else
        //in_addr only has 1 address
        struct in_addr * dest_ip_ptr = (struct in_addr *)CMSG_DATA(cmsg);
        dest_ip = dest_ip_ptr->_S_un._S_addr;
#endif
    }
}
if( ipaddr ) 
    ipaddr->IP = dest_ip;

//according to the Linux article mentioned below, the caddr should have the source
//socket address.  In my case, the caddr field is not filled with any coherent data,
//so this does not seem to be the source address.  Then again, "source socket" could
//be the interface IP on the local machine, which isn't what I need.

我也看过以下文章，但他们似乎没有回答我的问题： Get destination address of a received UDP packet，解决方案：Get destination address of a received UDP packet

Answer 1

有两个问题：一个是你不在任何地方使用caddr而你没有说它是什么，所以很难帮助你;另一个（可能是您遇到的问题）是您从recvmsg获得的地址不是字符串。

msg.msg_name应指向struct sockaddr_in，msg.msg_namelen应sizeof(struct sockaddr_in)。然后你从那里得到地址。

Solaris 10 - 从recvmsg（）获取UDP多播数据包的IP源地址

1 个答案: