RDMA连接

最新推荐文章于 2025-06-13 08:44:23 发布

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最新推荐文章于 2025-06-13 08:44:23 发布

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分类专栏： RDMA 文章标签：网络

本文链接：https://blog.youkuaiyun.com/qq_36537040/article/details/116152519

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本文详细介绍了RDMA连接的建立步骤，包括使用rdma_resolve_addr将目标IP地址转换为RDMA地址，以及通过rdma_resolve_route解析路由。在建立连接前，还需要对额外的资源进行初始化。

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RDMA连接的建立

rdma_resolve_addr用于将给定的目标 IP 地址映射到可用的 RDMA 地址

/* struct sockaddr_in *s_addr 代表ip地址 */
static struct rdma_event_channel *cm_event_channel = NULL;
static struct rdma_cm_id *cm_client_id = NULL;
/* 打开用于报告通信事件的事件通道。通过事件通道向用户报告异步事件 */
cm_event_channel = rdma_create_event_channel();

/* rdma_cm_ids 在概念上等同于 RDMA 通信的套接字。不同之处在于 RDMA 通信需
要在通信发生之前明确绑定到指定的 RDMA 设备，并且大多数操作本质上是异步的。*/
rdma_create_id(cm_event_channel, &cm_client_id, 
			NULL,
			RDMA_PS_TCP);
rdma_resolve_addr(cm_client_id, NULL, (struct sockaddr*) s_addr, 2000);

rdma_resolve_route用于将rdma地址解析为路由

struct rdma_cm_event *cm_event = NULL;

/* 等待channel上发生事件: RDMA_CM_EVENT_ADDR_RESOLVED */
process_rdma_cm_event(cm_event_channel, 
			RDMA_CM_EVENT_ADDR_RESOLVED,
			&cm_event);

/* 接受事件（在接受事件之前应该通过process_rdma_cn_event返回的结果判断此事件是否确实发生了） */
rdma_ack_cm_event(cm_event);

 /* 将目标RDMA地址解析为路由 */
rdma_resolve_route(cm_client_id, 2000);

/* 等待事件: RDMA_CM_EVENT_ROUTE_RESOLVED */
process_rdma_cm_event(cm_event_channel, 
			RDMA_CM_EVENT_ROUTE_RESOLVED,
			&cm_event);
rdma_ack_cm_event(cm_event);

在建立连接之前还需要初始化其他资源

/* All resources are tied to a particular PD. 
	 * And accessing recourses across PD will result in a protection fault. */
pd = ibv_alloc_pd(cm_client_id->verbs);


/* Now we need a completion channel, were the I/O completion 
	 * notifications are sent. Remember, this is different from connection 
	 * management (CM) event notifications. 
	 * A completion channel is also tied to an RDMA device, hence we will 
	 * use cm_client_id->verbs. */
io_completion_channel = ibv_create_comp_channel(cm_client_id->verbs);

/* Now we create a completion queue (CQ) where actual I/O 
	 * completion metadata is placed. The metadata is packed into a structure 
	 * called struct ibv_wc (wc = work completion). ibv_wc has detailed 
	 * information about the work completion. An I/O request in RDMA world 
	 * is called "work" ;) 
	 */
client_cq = ibv_create_cq(cm_client_id->verbs /* which device*/, 
			CQ_CAPACITY /* maximum capacity*/, 
			NULL /* user context, not used here */,
			io_completion_channel /* which IO completion channel */, 
			0 /* signaling vector, not used here*/);

/* 为cq提供通知机制 */
ibv_req_notify_cq(client_cq, 0);

/* create a qp with initial args qp_init_attr*/
rdma_create_qp(cm_client_id /* which connection id */,
		       pd /* which protection domain*/,
		       &qp_init_attr /* Initial attributes */);
client_qp = cm_client_id.qp;