RDMA是一种基于硬件的高性能网络技术，需要特殊的硬件设备和驱动程序支持。在Linux中，实现RDMA需要使用InfiniBand或RoCE适配器，安装相应的驱动程序，并使用libibverbs库进行编程。

以下是一个简单的示例代码，用于在两个节点之间通过RDMA传输数据：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#include <rdma/rdma_cma.h>

#define BUFFER_SIZE 1024

struct rdma_resources {
    struct rdma_cm_id *id;
    struct ibv_qp *qp;
    struct ibv_mr *mr;
    char *buffer;
};

void create_rdma_resources(struct rdma_event_channel *channel, 
                           struct sockaddr_in6 *addr, 
                           int port,
                           struct rdma_resources *resources) {

    // Create the RDMA communication identifier
    if (rdma_create_id(channel, &resources->id, NULL, RDMA_PS_TCP)) {
        perror("rdma_create_id");
        exit(1);
    }

    // Resolve the destination address
    if (rdma_resolve_addr(resources->id, NULL, (struct sockaddr*)addr, 1000)) {
        perror("rdma_resolve_addr");
        exit(1);
    }

    // Wait for address resolution to complete
    struct rdma_cm_event *event;
    while (rdma_get_cm_event(channel, &event) == 0) {
        if (event->event == RDMA_CM_EVENT_ADDR_RESOLVED) {
            rdma_ack_cm_event(event);
            break;
        }
        rdma_ack_cm_event(event);
    }

    // Resolve the route
    if (rdma_resolve_route(resources->id, 1000)) {
        perror("rdma_resolve_route");
        exit(1);
    }

    // Wait for route resolution to complete
    while (rdma_get_cm_event(channel, &event) == 0) {
        if (event->event == RDMA_CM_EVENT_ROUTE_RESOLVED) {
            rdma_ack_cm_event(event);
            break;
        }
        rdma_ack_cm_event(event);
    }

    // Create a queue pair
    struct ibv_qp_init_attr qp_attr = {0};
    qp_attr.send_cq = resources->id->send_cq;
    qp_attr.recv_cq = resources->id->recv_cq;
    qp_attr.qp_type = IBV_QPT_RC;

    if (rdma_create_qp(resources->id, NULL, &qp_attr)) {
        perror("rdma_create_qp");
        exit(1);
    }
    
    resources->qp = resources->id->qp;

     // Allocate memory for the buffer to be transferred
     resources->buffer = malloc(BUFFER_SIZE);

     if (!resources->buffer) {
         perror("malloc");
         exit(1);
     }

     memset(resources->buffer, 'a', BUFFER_SIZE);

     // Register the buffer with the HCA
     resources->mr = ibv_reg_mr(rdma_get_pd(resources->id), 
                                resources->buffer,
                                BUFFER_SIZE,
                                IBV_ACCESS_LOCAL_WRITE | IBV_ACCESS_REMOTE_READ | IBV_ACCESS_REMOTE_WRITE);

}

void destroy_rdma_resources(struct rdma_resources *resources) {

   // Free the buffer memory
   free(resources->buffer);

   // Destroy the queue pair
   rdma_destroy_qp(resources->id);

   // Destroy the RDMA communication identifier
   rdma_destroy_id(resources->id);
}

void send_rdma_data(struct rdma_resources *resources) {

    // Send a message to the remote host
    struct ibv_send_wr wr = {0};
    struct ibv_sge sge = {0};
    
    wr.wr_id = 0;
    wr.opcode = IBV_WR_SEND;
    wr.sg_list = &sge;
    wr.num_sge = 1;
    wr.send_flags = IBV_SEND_SIGNALED;

    sge.addr = (uint64_t)resources->buffer;
    sge.length = BUFFER_SIZE;
    sge.lkey = resources->mr->lkey;

     if (ibv_post_send(resources->qp, &wr, NULL)) {
         perror("ibv_post_send");
         exit(1);
     }
}

int main(int argc, char **argv) {

    if (argc != 3) {
        fprintf(stderr, "Usage: %s <hostname> <port>\n", argv[0]);
        exit(1);
    }

    // Parse command line arguments
    char *hostname = argv[1];
    int port = atoi(argv[2]);

     // Create an RDMA event channel
     struct rdma_event_channel *channel;
     
     if (!(channel = rdma_create_event_channel())) {
         perror("rdma_create_event_channel");
         exit(1);
     }

     // Get the IP address for the hostname
     struct addrinfo hints, *addr_list, *p;

     memset(&hints, 0, sizeof(hints));
     hints.ai_family = AF_INET6;
     hints.ai_socktype = SOCK_STREAM;

      if (getaddrinfo(hostname, NULL, &hints, &addr_list)) {
          perror("getaddrinfo");
          exit(1);
      }

      struct sockaddr_in6 addr;
      memset(&addr, 0, sizeof(addr));
      addr.sin6_family = AF_INET6;
      addr.sin6_port = htons(port);

     for (p = addr_list; p != NULL; p = p->ai_next) {
         if (p->ai_family == AF_INET6) {
             memcpy(&addr.sin6_addr, &((struct sockaddr_in6*)p->ai_addr)->sin6_addr, 
                    sizeof(struct in6_addr));
             break;
         }
     }

     // Create the RDMA resources
     struct rdma_resources resources;

     create_rdma_resources(channel, &addr, port, &resources);

     // Connect to the remote host
     if (rdma_connect(resources.id, NULL)) {
         perror("rdma_connect");
         exit(1);
     }

    // Send data using RDMA
    send_rdma_data(&resources);

    // Destroy the RDMA resources
    destroy_rdma_resources(&resources);

    // Clean up
    rdma_destroy_event_channel(channel);
    freeaddrinfo(addr_list);

    return 0;
}

这段代码演示了如何创建RDMA通信所需的资源，建立连接，并发送数据。请注意，此代码仅为示例目的，可能需要根据实际情况进行修改和扩展。


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