在Broadcom中提供了自己的消息机制，有两种消息形式：Request/Response and Event（事件）

Request/Response消息：进程之间的通信都是通过smd，所有的消息都是先发送到smd，smd收到信息后，如果消息目的是smd的就做相应的操作，如果不是，就把这个消息route出去

Event messages ：对某些事件感兴趣的进程，可以CMS_MSG_REGISTER_EVENT_INTEREST注册此感兴趣事件。事件发生时，将事件信息发送给smd，smd再将事件信息发送给感兴趣的进程。

1. smd与其他进程的通信的实现

smd监听消息

if ((fd = socket(AF_LOCAL, SOCK_STREAM, 0)) < 0)
{
cmsLog_error("Could not create socket");
return fd;
}

/*
* Bind my server address and listen.
*/
memset(&serverAddr, 0, sizeof(serverAddr));
serverAddr.sun_family = AF_LOCAL;
strncpy(serverAddr.sun_path, SMD_MESSAGE_ADDR, sizeof(serverAddr.sun_path));

rc = bind(fd, (struct sockaddr *) &serverAddr, sizeof(serverAddr));
if (rc != 0)
{
cmsLog_error("bind to %s failed, rc=%d errno=%d", SMD_MESSAGE_ADDR, rc, errno);
close(fd);
return -1;
}

rc = listen(fd, SMD_MESSAGE_BACKLOG);
if (rc != 0)
{
cmsLog_error("listen to %s failed, rc=%d errno=%d", SMD_MESSAGE_ADDR, rc, errno);
close(fd);
return -1;
}

其他进程连接到smd：cmsMsg_init

cmsMsg_init具体实现

/*
* Create a unix domain socket.
*/
handle->commFd = socket(AF_LOCAL, SOCK_STREAM, 0);
if (handle->commFd < 0)
{
cmsLog_error("Could not create socket");
cmsMem_free(handle);
return CMSRET_INTERNAL_ERROR;
}

/*
* Set close-on-exec, even though all apps should close their
* fd‘s before fork and exec.
*/
if ((rc = fcntl(handle->commFd, F_SETFD, FD_CLOEXEC)) != 0)
{
cmsLog_error("set close-on-exec failed, rc=%d errno=%d", rc, errno);
close(handle->commFd);
cmsMem_free(handle);
return CMSRET_INTERNAL_ERROR;
}

/*
* Connect to smd.
*/
memset(&serverAddr, 0, sizeof(serverAddr));
serverAddr.sun_family = AF_LOCAL;
strncpy(serverAddr.sun_path, SMD_MESSAGE_ADDR, sizeof(serverAddr.sun_path));

rc = connect(handle->commFd, (struct sockaddr *) &serverAddr, sizeof(serverAddr));
if (rc != 0)
{
cmsLog_error("connect to %s failed, rc=%d errno=%d", SMD_MESSAGE_ADDR, rc, errno);
close(handle->commFd);
cmsMem_free(handle);
return CMSRET_INTERNAL_ERROR;
}
else
{
cmsLog_debug("commFd=%d connected to smd", handle->commFd);
}

这样就建立了其他进程与smd的连接，阻塞等待事件的发生

/* pend, waiting for one or more fds to become ready */
rv = select(maxFd+1, &readFds, NULL, NULL, &tm);

用cmsMsg_send cmsMsg_receive发送接收信息，事件发生之后，processMessage处理信息

2. 与kernel的通信

底层 atm, dsl, eth 状态发生改变的时候，会发信息给ssk，ssk再把信息发送给smd

/*
* Initialize special socket to kernel for WAN link-up, link-down events.
* The kernel notification mechanism uses the error channel of some existing fd.
* See webmain in cfm/web.
*/
if ((ret = initKernelMonitorFd()) != CMSRET_SUCCESS)

initKernelMonitorFd：

if ((kernelMonitorFd = socket(AF_NETLINK, SOCK_RAW, NETLINK_BRCM_MONITOR)) < 0)
//if ((kernelMonitorFd = socket(AF_NETLINK, SOCK_RAW, NETLINK_UNUSED)) < 0)
{
cmsLog_error("Could not open netlink socket for kernel monitor");
return CMSRET_INTERNAL_ERROR;
}
else
{
cmsLog_debug("kernelMonitorFd=%d", kernelMonitorFd);
}

addr.nl_family = AF_NETLINK;
addr.nl_pid = getpid();
addr.nl_groups = 0;

if (bind(kernelMonitorFd,(struct sockaddr *)&addr,sizeof(addr))<0)
{
cmsLog_error("Could not bind netlink socket for kernel monitor");
close(kernelMonitorFd);
kernelMonitorFd = CMS_INVALID_FD;
return CMSRET_INTERNAL_ERROR;
}

然后将kernelMonitorFd  加入select集中，阻塞n = select(maxFd+1, &readFds, NULL, &errorFds, &tv);

if (FD_ISSET(kernelMonitorFd, &readFds))
{
processKernelMonitor();
}

processKernelMonitor：轮询信息

/* There can be more than one message per recvmsg */
for(nl_msgHdr = (struct nlmsghdr *) buf; NLMSG_OK (nl_msgHdr, (unsigned int)recvLen);
nl_msgHdr = NLMSG_NEXT (nl_msgHdr, recvLen))

3. 事件消息

首先需要注册感兴趣的事件

msg->type = CMS_MSG_REGISTER_EVENT_INTEREST;
msg->flags_request = 1;
msg->flags_response = 0;
msg->flags_event = 0;
msg->wordData = http://www.mamicode.com/CMS_MSG_DHCP6C_STATE_CHANGED;
if ((ret = cmsMsg_sendAndGetReply(msgHandle, msg)) != CMSRET_SUCCESS)
{

}

当dhcp6c发生改变的时候，发送事件信息到smd

msg->type = CMS_MSG_DHCP6C_STATE_CHANGED;
msg->src = http://www.mamicode.com/MAKE_SPECIFIC_EID(getpid(), EID_DHCP6C);
msg->dst = EID_SMD;
msg->flags_event = 1;
msg->dataLength = sizeof(Dhcp6cStateChangedMsgBody);

memcpy(dhcp6cBody, &dhcp6cMsgBody, sizeof(Dhcp6cStateChangedMsgBody));

if ((ret = cmsMsg_send(msgHandle, msg)) != CMSRET_SUCCESS)

smd收到事件信息之后，查找感兴趣的进程将信息发送出去

distributeEventMessage

这里CMS_MSG_DHCP6C_STATE_CHANGED是在ssk注册的，所以到ssk，ssk收到信息之后

#ifdef DMP_X_BROADCOM_COM_IPV6_1 /* aka SUPPORT_IPV6 */
case CMS_MSG_DHCP6C_STATE_CHANGED:
processDhcp6cStateChanged(msg);
break;

Broadcom的消息机制