8.2 发送、接收、RDMA 读取、RDMA 写入的代码

示例代码

/*
* BUILD COMMAND:
* gcc -Wall -I/usr/local/ofed/include -O2 -o RDMA_RC_example -L/usr/local/
ofed/lib64 -L/usr/local/ofed/lib -libverbs RDMA_RC_example.c
*
* Usage:
* RDMA_RC_example --help
*/
/******************************************************************************
*
* RDMA Aware Networks Programming Example
*
* This code demonstrates how to perform the following operations using the
* VPI Verbs API:
*
* Send
* Receive
* RDMA Read
* RDMA Write
*
*****************************************************************************/
#include <arpa/inet.h>
#include <byteswap.h>
#include <endian.h>
#include <getopt.h>
#include <infiniband/verbs.h>
#include <inttypes.h>
#include <netdb.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
/* poll CQ timeout in millisec (2 seconds) */
#define MAX_POLL_CQ_TIMEOUT 2000
#define MSG      "SEND operation      "
#define RDMAMSGR "RDMA read operation "
#define RDMAMSGW "RDMA write operation"
#define MSG_SIZE (strlen(MSG) + 1)
#if __BYTE_ORDER == __LITTLE_ENDIAN
static inline uint64_t htonll(uint64_t x) { return bswap_64(x); }
static inline uint64_t ntohll(uint64_t x) { return bswap_64(x); }
#elif __BYTE_ORDER == __BIG_ENDIAN
static inline uint64_t htonll(uint64_t x) { return x; }
static inline uint64_t ntohll(uint64_t x) { return x; }
#else
#error __BYTE_ORDER is neither __LITTLE_ENDIAN nor __BIG_ENDIAN
#endif

/* structure of test parameters */
struct config_t
{
    const char *dev_name; /* IB device name */
    char *server_name;    /* server host name */
    u_int32_t tcp_port;   /* server TCP port */
    int ib_port;          /* local IB port to work with */
    int gid_idx;          /* gid index to use */
};

/* structure to exchange data which is needed to connect the QPs */
struct cm_con_data_t
{
    uint64_t addr;   /* Buffer address */
    uint32_t rkey;   /* Remote key */
    uint32_t qp_num; /* QP number */
    uint16_t lid;    /* LID of the IB port */
    uint8_t gid[16]; /* gid */
} __attribute__((packed));

/* structure of system resources */
struct resources
{
    struct ibv_device_attr device_attr;
    /* Device attributes */
    struct ibv_port_attr port_attr;    /* IB port attributes */
    struct cm_con_data_t remote_props; /* values to connect to remote side */
    struct ibv_context *ib_ctx;        /* device handle */
    struct ibv_pd *pd;                 /* PD handle */
    struct ibv_cq *cq;                 /* CQ handle */
    struct ibv_qp *qp;                 /* QP handle */
    struct ibv_mr *mr;                 /* MR handle for buf */
    char *buf;                         /* memory buffer pointer, used for RDMA and send ops */
    int sock;                          /* TCP socket file descriptor */
};

struct config_t config = {
    NULL,  /* dev_name */
    NULL,  /* server_name */
    19875, /* tcp_port */
    1,     /* ib_port */
    -1     /* gid_idx */
};

/******************************************************************************
Socket operations
For simplicity, the example program uses TCP sockets to exchange control
information. If a TCP/IP stack/connection is not available, connection manager
(CM) may be used to pass this information. Use of CM is beyond the scope of
this example
******************************************************************************/

/******************************************************************************
 * Function: sock_connect
 *
 * Input
 * servername URL of server to connect to (NULL for server mode)
 * port port of service
 *
 * Output
 * none
 *
 * Returns
 * socket (fd) on success, negative error code on failure
 *
 * Description
 * Connect a socket. If servername is specified a client connection will be
 * initiated to the indicated server and port. Otherwise listen on the
 * indicated port for an incoming connection.
 *
 ******************************************************************************/

static int sock_connect(const char *servername, int port)
{
    // `struct addrinfo' is not part of standard C, but belongs to gnu.
    // https://stackoverflow.com/questions/33076175/why-is-struct-addrinfo-defined-only-if-use-xopen2k-is-defined
    struct addrinfo *resolved_addr = NULL;
    struct addrinfo *iterator;
    char service[6];
    int sockfd = -1;
    int listenfd = 0;
    int tmp;

    struct addrinfo hints = {
        .ai_flags = AI_PASSIVE, .ai_family = AF_INET, .ai_socktype = SOCK_STREAM};
    if (sprintf(service, "%d", port) < 0)
        goto sock_connect_exit;
    /* Resolve DNS address, use sockfd as temp storage */
    sockfd = getaddrinfo(servername, service, &hints, &resolved_addr);
    if (sockfd < 0)
    {
        fprintf(stderr, "%s for %s:%d\n", gai_strerror(sockfd), servername, port);
        goto sock_connect_exit;
    }
    /* Search through results and find the one we want */
    for (iterator = resolved_addr; iterator; iterator = iterator->ai_next)
    {
        sockfd = socket(iterator->ai_family, iterator->ai_socktype,
                        iterator->ai_protocol);
        if (sockfd >= 0)
        {
            if (servername)
            {
                /* Client mode. Initiate connection to remote */
                if ((tmp = connect(sockfd, iterator->ai_addr, iterator->ai_addrlen)))
                {
                    fprintf(stdout, "failed connect \n");
                    close(sockfd);
                    sockfd = -1;
                }
            }
            else
            {
                /* Server mode. Set up listening socket an accept a connection
                 */
                listenfd = sockfd;
                sockfd = -1;
                if (bind(listenfd, iterator->ai_addr, iterator->ai_addrlen))
                    goto sock_connect_exit;
                listen(listenfd, 1);
                sockfd = accept(listenfd, NULL, 0);
            }
        }
    }
sock_connect_exit:
    if (listenfd)
        close(listenfd);
    if (resolved_addr)
        freeaddrinfo(resolved_addr);
    if (sockfd < 0)
    {
        if (servername)
            fprintf(stderr, "Couldn't connect to %s:%d\n", servername, port);
        else
        {
            perror("server accept");
            fprintf(stderr, "accept() failed\n");
        }
    }
    return sockfd;
}

/******************************************************************************
* Function: sock_sync_data
*
* Input
* sock socket to transfer data on
* xfer_size size of data to transfer
* local_data pointer to data to be sent to remote
*
* Output
* remote_data pointer to buffer to receive remote data
*
* Returns
* 0 on success, negative error code on failure
*
* Description
* Sync data across a socket. The indicated local data will be sent to the
* remote. It will then wait for the remote to send its data back. It is
* assumed that the two sides are in sync and call this function in the proper
* order. Chaos will ensue if they are not. :)
*
* Also note this is a blocking function and will wait for the full data to be
* received from the remote.
*
******************************************************************************/
int sock_sync_data(int sock, int xfer_size, char *local_data,
                   char *remote_data)
{
    int rc;
    int read_bytes = 0;
    int total_read_bytes = 0;
    rc = write(sock, local_data, xfer_size);
    if (rc < xfer_size)
        fprintf(stderr, "Failed writing data during sock_sync_data\n");
    else
        rc = 0;
    while (!rc && total_read_bytes < xfer_size)
    {
        read_bytes = read(sock, remote_data, xfer_size);
        if (read_bytes > 0)
            total_read_bytes += read_bytes;
        else
            rc = read_bytes;
    }
    return rc;
}

/******************************************************************************
End of socket operations
******************************************************************************/

/* poll_completion */
/******************************************************************************
 * Function: poll_completion
 *
 * Input
 * res pointer to resources structure
 *
 * Output
 * none
 *
 * Returns
 * 0 on success, 1 on failure
 *
 * Description
 * Poll the completion queue for a single event. This function will continue to
 * poll the queue until MAX_POLL_CQ_TIMEOUT milliseconds have passed.
 *
 ******************************************************************************/
static int poll_completion(struct resources *res)
{
    struct ibv_wc wc;
    unsigned long start_time_msec;
    unsigned long cur_time_msec;
    struct timeval cur_time;
    int poll_result;
    int rc = 0;
    /* poll the completion for a while before giving up of doing it .. */
    gettimeofday(&cur_time, NULL);
    start_time_msec = (cur_time.tv_sec * 1000) + (cur_time.tv_usec / 1000);
    do
    {
        poll_result = ibv_poll_cq(res->cq, 1, &wc);
        gettimeofday(&cur_time, NULL);
        cur_time_msec = (cur_time.tv_sec * 1000) + (cur_time.tv_usec / 1000);
    } while ((poll_result == 0) &&
             ((cur_time_msec - start_time_msec) < MAX_POLL_CQ_TIMEOUT));
    if (poll_result < 0)
    {
        /* poll CQ failed */
        fprintf(stderr, "poll CQ failed\n");
        rc = 1;
    }
    else if (poll_result == 0)
    {
        /* the CQ is empty */
        fprintf(stderr, "completion wasn't found in the CQ after timeout\n");
        rc = 1;
    }
    else
    {
        /* CQE found */
        fprintf(stdout, "completion was found in CQ with status 0x%x\n", wc.status);
        /* check the completion status (here we don't care about the completion
        opcode */
        if (wc.status != IBV_WC_SUCCESS)
        {
            fprintf(stderr, "got bad completion with status: 0x%x, vendor syndrome: 0x%x\n", wc.status, wc.vendor_err);
            rc = 1;
        }
    }
    return rc;
}

/******************************************************************************
 * Function: post_send
 *
 * Input
 * res pointer to resources structure
 * opcode IBV_WR_SEND, IBV_WR_RDMA_READ or IBV_WR_RDMA_WRITE
 *
 * Output
 * none
 *
 * Returns
 * 0 on success, error code on failure
 *
 * Description
 * This function will create and post a send work request
 ******************************************************************************/
static int post_send(struct resources *res, int opcode)
{
    struct ibv_send_wr sr;
    struct ibv_sge sge;
    struct ibv_send_wr *bad_wr = NULL;
    int rc;

    /* prepare the scatter/gather entry */
    memset(&sge, 0, sizeof(sge));
    sge.addr = (uintptr_t)res->buf;
    sge.length = MSG_SIZE;
    sge.lkey = res->mr->lkey;
    /* prepare the send work request */
    memset(&sr, 0, sizeof(sr));
    sr.next = NULL;
    sr.wr_id = 0;
    sr.sg_list = &sge;
    sr.num_sge = 1;
    sr.opcode = opcode;
    sr.send_flags = IBV_SEND_SIGNALED;
    if (opcode != IBV_WR_SEND)
    {
        sr.wr.rdma.remote_addr = res->remote_props.addr;
        sr.wr.rdma.rkey = res->remote_props.rkey;
    }
    /* there is a Receive Request in the responder side, so we won't get any
    into RNR flow */
    rc = ibv_post_send(res->qp, &sr, &bad_wr);
    if (rc)
        fprintf(stderr, "failed to post SR\n");
    else
    {
        switch (opcode)
        {
        case IBV_WR_SEND:
            fprintf(stdout, "Send Request was posted\n");
            break;
        case IBV_WR_RDMA_READ:
            fprintf(stdout, "RDMA Read Request was posted\n");
            break;
        case IBV_WR_RDMA_WRITE:
            fprintf(stdout, "RDMA Write Request was posted\n");
            break;
        default:
            fprintf(stdout, "Unknown Request was posted\n");
            break;
        }
    }
    return rc;
}

/******************************************************************************
 * Function: post_receive
 *
 * Input
 * res pointer to resources structure
 *
 * Output
 * none
 *
 * Returns
 * 0 on success, error code on failure
 *
 * Description
 *
 ******************************************************************************/
static int post_receive(struct resources *res)
{
    struct ibv_recv_wr rr;
    struct ibv_sge sge;
    struct ibv_recv_wr *bad_wr;
    int rc;
    /* prepare the scatter/gather entry */
    memset(&sge, 0, sizeof(sge));
    sge.addr = (uintptr_t)res->buf;
    sge.length = MSG_SIZE;
    sge.lkey = res->mr->lkey;
    /* prepare the receive work request */
    memset(&rr, 0, sizeof(rr));
    rr.next = NULL;
    rr.wr_id = 0;
    rr.sg_list = &sge;
    rr.num_sge = 1;
    /* post the Receive Request to the RQ */
    rc = ibv_post_recv(res->qp, &rr, &bad_wr);
    if (rc)
        fprintf(stderr, "failed to post RR\n");
    else
        fprintf(stdout, "Receive Request was posted\n");
    return rc;
}

/******************************************************************************
 * Function: resources_init
 *
 * Input
 * res pointer to resources structure
 *
 * Output
 * res is initialized
 *
 * Returns
 * none
 *
 * Description
 * res is initialized to default values
 ******************************************************************************/
static void resources_init(struct resources *res)
{
    memset(res, 0, sizeof *res);
    res->sock = -1;
}

/******************************************************************************
 * Function: resources_create
 *
 * Input
 * res pointer to resources structure to be filled in
 *
 * Output
 * res filled in with resources
 *
 * Returns
 * 0 on success, 1 on failure
 *
 * Description
 *
 * This function creates and allocates all necessary system resources. These
 * are stored in res.
 *****************************************************************************/
static int resources_create(struct resources *res)
{
    struct ibv_device **dev_list = NULL;
    struct ibv_qp_init_attr qp_init_attr;
    struct ibv_device *ib_dev = NULL;
    size_t size;
    int i;
    int mr_flags = 0;
    int cq_size = 0;
    int num_devices;
    int rc = 0;

    /* if client side */
    if (config.server_name)
    {
        res->sock = sock_connect(config.server_name, config.tcp_port);
        if (res->sock < 0)
        {
            fprintf(stderr,
                    "failed to establish TCP connection to server %s, port %d\n ",
                    config.server_name,
                    config.tcp_port);
            rc = -1;
            goto resources_create_exit;
        }
    }
    else
    {
        fprintf(stdout, "waiting on port %d for TCP connection\n", config.tcp_port);
        res->sock = sock_connect(NULL, config.tcp_port);
        if (res->sock < 0)
        {
            fprintf(stderr, "failed to establish TCP connection with client on port %d\n ", config.tcp_port);
            rc = -1;
            goto resources_create_exit;
        }
    }
    fprintf(stdout, "TCP connection was established\n");
    fprintf(stdout, "searching for IB devices in host\n");
    /* get device names in the system */
    dev_list = ibv_get_device_list(&num_devices);
    if (!dev_list)
    {
        fprintf(stderr, "failed to get IB devices list\n");
        rc = 1;
        goto resources_create_exit;
    }
    /* if there isn't any IB device in host */
    if (!num_devices)
    {
        fprintf(stderr, "found %d device(s)\n", num_devices);
        rc = 1;
        goto resources_create_exit;
    }
    fprintf(stdout, "found %d device(s)\n", num_devices);
    /* search for the specific device we want to work with */
    for (i = 0; i < num_devices; i++)
    {
        if (!config.dev_name)
        {
            config.dev_name = strdup(ibv_get_device_name(dev_list[i]));
            fprintf(stdout, "device not specified, using first one found: %s\n", config.dev_name);
        }
        if (!strcmp(ibv_get_device_name(dev_list[i]), config.dev_name))
        {
            ib_dev = dev_list[i];
            break;
        }
    }
    /* if the device wasn't found in host */
    if (!ib_dev)
    {
        fprintf(stderr, "IB device %s wasn't found\n", config.dev_name);
        rc = 1;
        goto resources_create_exit;
    }
    /* get device handle */
    res->ib_ctx = ibv_open_device(ib_dev);
    if (!res->ib_ctx)
    {
        fprintf(stderr, "failed to open device %s\n", config.dev_name);
        rc = 1;
        goto resources_create_exit;
    }
    /* We are now done with device list, free it */
    ibv_free_device_list(dev_list);
    dev_list = NULL;
    ib_dev = NULL;
    /* query port properties */
    if (ibv_query_port(res->ib_ctx, config.ib_port, &res->port_attr))
    {
        fprintf(stderr, "ibv_query_port on port %u failed\n", config.ib_port);
        rc = 1;
        goto resources_create_exit;
    }
    /* allocate Protection Domain */
    res->pd = ibv_alloc_pd(res->ib_ctx);
    if (!res->pd)
    {
        fprintf(stderr, "ibv_alloc_pd failed\n");
        rc = 1;
        goto resources_create_exit;
    }
    /* each side will send only one WR, so Completion Queue with 1 entry is
    enough */
    cq_size = 1;
    res->cq = ibv_create_cq(res->ib_ctx, cq_size, NULL, NULL, 0);
    if (!res->cq)
    {
        fprintf(stderr, "failed to create CQ with %u entries\n", cq_size);
        rc = 1;
        goto resources_create_exit;
    }
    /* allocate the memory buffer that will hold the data */
    size = MSG_SIZE;
    res->buf = (char *)malloc(size);
    if (!res->buf)
    {
        fprintf(stderr, "failed to malloc %zu bytes to memory buffer\n", size);
        rc = 1;
        goto resources_create_exit;
    }
    memset(res->buf, 0, size);
    /* only in the server side put the message in the memory buffer */
    if (!config.server_name)
    {
        strcpy(res->buf, MSG);
        fprintf(stdout, "going to send the message: '%s'\n", res->buf);
    }
    else
        memset(res->buf, 0, size);
    /* register the memory buffer */
    mr_flags =
        IBV_ACCESS_LOCAL_WRITE | IBV_ACCESS_REMOTE_READ | IBV_ACCESS_REMOTE_WRITE;
    res->mr = ibv_reg_mr(res->pd, res->buf, size, mr_flags);
    if (!res->mr)
    {
        fprintf(stderr, "ibv_reg_mr failed with mr_flags=0x%x\n", mr_flags);
        rc = 1;
        goto resources_create_exit;
    }
    fprintf(stdout,
            "MR was registered with addr=%p, lkey=0x%x, rkey=0x%x, flags=0x%x\n",
            res->buf, res->mr->lkey, res->mr->rkey, mr_flags);
    /* create the Queue Pair */
    memset(&qp_init_attr, 0, sizeof(qp_init_attr));
    qp_init_attr.qp_type = IBV_QPT_RC;
    qp_init_attr.sq_sig_all = 1;
    qp_init_attr.send_cq = res->cq;
    qp_init_attr.recv_cq = res->cq;
    qp_init_attr.cap.max_send_wr = 1;
    qp_init_attr.cap.max_recv_wr = 1;
    qp_init_attr.cap.max_send_sge = 1;
    qp_init_attr.cap.max_recv_sge = 1;
    res->qp = ibv_create_qp(res->pd, &qp_init_attr);
    if (!res->qp)
    {
        fprintf(stderr, "failed to create QP\n");
        rc = 1;
        goto resources_create_exit;
    }
    fprintf(stdout, "QP was created, QP number=0x%x\n", res->qp->qp_num);
resources_create_exit:
    if (rc)
    {
        /* Error encountered, cleanup */
        if (res->qp)
        {
            ibv_destroy_qp(res->qp);
            res->qp = NULL;
        }
        if (res->mr)
        {
            ibv_dereg_mr(res->mr);
            res->mr = NULL;
        }
        if (res->buf)
        {
            free(res->buf);
            res->buf = NULL;
        }
        if (res->cq)
        {
            ibv_destroy_cq(res->cq);
            res->cq = NULL;
        }
        if (res->pd)
        {
            ibv_dealloc_pd(res->pd);
            res->pd = NULL;
        }
        if (res->ib_ctx)
        {
            ibv_close_device(res->ib_ctx);
            res->ib_ctx = NULL;
        }
        if (dev_list)
        {
            ibv_free_device_list(dev_list);
            dev_list = NULL;
        }
        if (res->sock >= 0)
        {
            if (close(res->sock))
                fprintf(stderr, "failed to close socket\n");
            res->sock = -1;
        }
    }
    return rc;
}

/******************************************************************************
 * Function: modify_qp_to_init
 *
 * Input
 * qp QP to transition
 *
 * Output
 * none
 *
 * Returns
 * 0 on success, ibv_modify_qp failure code on failure
 *
 * Description
 * Transition a QP from the RESET to INIT state
 ******************************************************************************/
static int modify_qp_to_init(struct ibv_qp *qp)
{
    struct ibv_qp_attr attr;
    int flags;
    int rc;
    memset(&attr, 0, sizeof(attr));
    attr.qp_state = IBV_QPS_INIT;
    attr.port_num = config.ib_port;
    attr.pkey_index = 0;
    attr.qp_access_flags =
        IBV_ACCESS_LOCAL_WRITE | IBV_ACCESS_REMOTE_READ | IBV_ACCESS_REMOTE_WRITE;
    flags = IBV_QP_STATE | IBV_QP_PKEY_INDEX | IBV_QP_PORT | IBV_QP_ACCESS_FLAGS;
    rc = ibv_modify_qp(qp, &attr, flags);
    if (rc)
        fprintf(stderr, "failed to modify QP state to INIT\n");
    return rc;
}

/******************************************************************************
 * Function: modify_qp_to_rtr
 *
 * Input
 * qp QP to transition
 * remote_qpn remote QP number
 * dlid destination LID
 * dgid destination GID (mandatory for RoCEE)
 *
 * Output
 * none
 *
 * Returns
 * 0 on success, ibv_modify_qp failure code on failure
 *
 * Description
 * Transition a QP from the INIT to RTR state, using the specified QP number
 ******************************************************************************/
static int modify_qp_to_rtr(struct ibv_qp *qp, uint32_t remote_qpn,
                            uint16_t dlid, uint8_t *dgid)
{
    struct ibv_qp_attr attr;
    int flags;
    int rc;
    memset(&attr, 0, sizeof(attr));
    attr.qp_state = IBV_QPS_RTR;
    attr.path_mtu = IBV_MTU_256;
    attr.dest_qp_num = remote_qpn;
    attr.rq_psn = 0;
    attr.max_dest_rd_atomic = 1;
    attr.min_rnr_timer = 0x12;
    attr.ah_attr.is_global = 0;
    attr.ah_attr.dlid = dlid;
    attr.ah_attr.sl = 0;
    attr.ah_attr.src_path_bits = 0;
    attr.ah_attr.port_num = config.ib_port;
    if (config.gid_idx >= 0)
    {
        attr.ah_attr.is_global = 1;
        attr.ah_attr.port_num = 1;
        memcpy(&attr.ah_attr.grh.dgid, dgid, 16);
        attr.ah_attr.grh.flow_label = 0;
        attr.ah_attr.grh.hop_limit = 1;
        attr.ah_attr.grh.sgid_index = config.gid_idx;
        attr.ah_attr.grh.traffic_class = 0;
    }
    flags = IBV_QP_STATE | IBV_QP_AV | IBV_QP_PATH_MTU | IBV_QP_DEST_QPN |
            IBV_QP_RQ_PSN | IBV_QP_MAX_DEST_RD_ATOMIC | IBV_QP_MIN_RNR_TIMER;
    rc = ibv_modify_qp(qp, &attr, flags);
    if (rc)
        fprintf(stderr, "failed to modify QP state to RTR\n");
    return rc;
}

/******************************************************************************
 * Function: modify_qp_to_rts
 *
 * Input
 * qp QP to transition
 *
 * Output
 * none
 *
 * Returns
 * 0 on success, ibv_modify_qp failure code on failure
 *
 * Description
 * Transition a QP from the RTR to RTS state
 ******************************************************************************/
static int modify_qp_to_rts(struct ibv_qp *qp)
{
    struct ibv_qp_attr attr;
    int flags;
    int rc;
    memset(&attr, 0, sizeof(attr));
    attr.qp_state = IBV_QPS_RTS;
    attr.timeout = 0x12;
    attr.retry_cnt = 6;
    attr.rnr_retry = 0;
    attr.sq_psn = 0;
    attr.max_rd_atomic = 1;
    flags = IBV_QP_STATE | IBV_QP_TIMEOUT | IBV_QP_RETRY_CNT | IBV_QP_RNR_RETRY |
            IBV_QP_SQ_PSN | IBV_QP_MAX_QP_RD_ATOMIC;
    rc = ibv_modify_qp(qp, &attr, flags);
    if (rc)
        fprintf(stderr, "failed to modify QP state to RTS\n");
    return rc;
}

/******************************************************************************
 * Function: connect_qp
 *
 * Input
 * res pointer to resources structure
 *
 * Output
 * none
 *
 * Returns
 * 0 on success, error code on failure
 *
 * Description
 * Connect the QP. Transition the server side to RTR, sender side to RTS
 ******************************************************************************/
static int connect_qp(struct resources *res)
{
    struct cm_con_data_t local_con_data;
    struct cm_con_data_t remote_con_data;
    struct cm_con_data_t tmp_con_data;
    int rc = 0;
    char temp_char;
    union ibv_gid my_gid;
    if (config.gid_idx >= 0)
    {
        rc = ibv_query_gid(res->ib_ctx, config.ib_port, config.gid_idx, &my_gid);
        if (rc)
        {
            fprintf(stderr, "could not get gid for port %d, index %d\n",
                    config.ib_port, config.gid_idx);
            return rc;
        }
    }
    else
        memset(&my_gid, 0, sizeof my_gid);
    /* exchange using TCP sockets info required to connect QPs */
    local_con_data.addr = htonll((uintptr_t)res->buf);
    local_con_data.rkey = htonl(res->mr->rkey);
    local_con_data.qp_num = htonl(res->qp->qp_num);
    local_con_data.lid = htons(res->port_attr.lid);
    memcpy(local_con_data.gid, &my_gid, 16);
    fprintf(stdout, "\nLocal LID = 0x%x\n", res->port_attr.lid);
    if (sock_sync_data(res->sock, sizeof(struct cm_con_data_t),
                       (char *)&local_con_data, (char *)&tmp_con_data) < 0)
    {
        fprintf(stderr, "failed to exchange connection data between sides\n");
        rc = 1;
        goto connect_qp_exit;
    }
    remote_con_data.addr = ntohll(tmp_con_data.addr);
    remote_con_data.rkey = ntohl(tmp_con_data.rkey);
    remote_con_data.qp_num = ntohl(tmp_con_data.qp_num);
    remote_con_data.lid = ntohs(tmp_con_data.lid);
    memcpy(remote_con_data.gid, tmp_con_data.gid, 16);
    /* save the remote side attributes, we will need it for the post SR */
    res->remote_props = remote_con_data;
    fprintf(stdout, "Remote address = 0x%" PRIx64 "\n", remote_con_data.addr);
    fprintf(stdout, "Remote rkey = 0x%x\n", remote_con_data.rkey);
    fprintf(stdout, "Remote QP number = 0x%x\n", remote_con_data.qp_num);
    fprintf(stdout, "Remote LID = 0x%x\n", remote_con_data.lid);
    if (config.gid_idx >= 0)
    {
        uint8_t *p = remote_con_data.gid;
        fprintf(stdout, "Remote GID = %02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x\n",
                p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7], p[8], p[9], p[10], p[11], p[12], p[13], p[14], p[15]);
    }
    /* modify the QP to init */
    rc = modify_qp_to_init(res->qp);
    if (rc)
    {
        fprintf(stderr, "change QP state to INIT failed\n");
        goto connect_qp_exit;
    }
    /* let the client post RR to be prepared for incoming messages */
    if (config.server_name)
    {
        rc = post_receive(res);
        if (rc)
        {
            fprintf(stderr, "failed to post RR\n");
            goto connect_qp_exit;
        }
    }
    /* modify the QP to RTR */
    rc = modify_qp_to_rtr(res->qp, remote_con_data.qp_num, remote_con_data.lid,
                          remote_con_data.gid);
    if (rc)
    {
        fprintf(stderr, "failed to modify QP state to RTR\n");
        goto connect_qp_exit;
    }
    rc = modify_qp_to_rts(res->qp);
    if (rc)
    {
        fprintf(stderr, "failed to modify QP state to RTR\n");
        goto connect_qp_exit;
    }
    fprintf(stdout, "QP state was change to RTS\n");
    /* sync to make sure that both sides are in states that they can connect
    to prevent packet loose */
    if (sock_sync_data(res->sock, 1, "Q", &temp_char)) /* just send a dummy
    char back and forth */
    {
        fprintf(stderr, "sync error after QPs are were moved to RTS\n");
        rc = 1;
    }
connect_qp_exit:
    return rc;
}

/******************************************************************************
 * Function: resources_destroy
 *
 * Input
 * res pointer to resources structure
 *
 * Output
 * none
 *
 * Returns
 * 0 on success, 1 on failure
 *
 * Description
 * Cleanup and deallocate all resources used
 ******************************************************************************/
static int resources_destroy(struct resources *res)
{
    int rc = 0;
    if (res->qp)
        if (ibv_destroy_qp(res->qp))
        {
            fprintf(stderr, "failed to destroy QP\n");
            rc = 1;
        }
    if (res->mr)
        if (ibv_dereg_mr(res->mr))
        {
            fprintf(stderr, "failed to deregister MR\n");
            rc = 1;
        }
    if (res->buf)
        free(res->buf);
    if (res->cq)
        if (ibv_destroy_cq(res->cq))
        {
            fprintf(stderr, "failed to destroy CQ\n");
            rc = 1;
        }
    if (res->pd)
        if (ibv_dealloc_pd(res->pd))
        {
            fprintf(stderr, "failed to deallocate PD\n");
            rc = 1;
        }
    if (res->ib_ctx)
        if (ibv_close_device(res->ib_ctx))
        {
            fprintf(stderr, "failed to close device context\n");
            rc = 1;
        }
    if (res->sock >= 0)
        if (close(res->sock))
        {
            fprintf(stderr, "failed to close socket\n");
            rc = 1;
        }
    return rc;
}

/******************************************************************************
 * Function: print_config
 *
 * Input
 * none
 *
 * Output
 * none
 *
 * Returns
 * none
 *
 * Description
 * Print out config information
 ******************************************************************************/
static void print_config(void)
{
    fprintf(stdout, " ------------------------------------------------\n");
    fprintf(stdout, " Device name : \"%s\"\n", config.dev_name);
    fprintf(stdout, " IB port : %u\n", config.ib_port);
    if (config.server_name)
        fprintf(stdout, " IP : %s\n", config.server_name);
    fprintf(stdout, " TCP port : %u\n", config.tcp_port);
    if (config.gid_idx >= 0)
        fprintf(stdout, " GID index : %u\n", config.gid_idx);
    fprintf(stdout, " ------------------------------------------------\n\n");
}

/******************************************************************************
 * Function: usage
 *
 * Input
 * argv0 command line arguments
 *
 * Output
 * none
 *
 * Returns
 * none
 *
 * Description
 * print a description of command line syntax
 ******************************************************************************/
static void usage(const char *argv0)
{
    fprintf(stdout, "Usage:\n");
    fprintf(stdout, " %s start a server and wait for connection\n", argv0);
    fprintf(stdout, " %s <host> connect to server at <host>\n", argv0);
    fprintf(stdout, "\n");
    fprintf(stdout, "Options:\n");
    fprintf(stdout, " -p, --port <port> listen on/connect to port <port> (default 18515)\n");
    fprintf(stdout, " -d, --ib-dev <dev> use IB device <dev> (default first device found)\n");
    fprintf(stdout, " -i, --ib-port <port> use port <port> of IB device (default 1)\n");
    fprintf(stdout, " -g, --gid_idx <git index> gid index to be used in GRH (default not used)\n");
    fprintf(stdout, " -h, --help\n");
}

/******************************************************************************
 * Function: main
 *
 * Input
 * argc number of items in argv
 * argv command line parameters
 *
 * Output
 * none
 *
 * Returns
 * 0 on success, 1 on failure
 *
 * Description
 * Main program code
 ******************************************************************************/
int main(int argc, char *argv[])
{
    struct resources res;
    int rc = 1;
    char temp_char;

    /* parse the command line parameters */
    while (1)
    {
        int c;
        static struct option long_options[] = {
            {.name = "port", .has_arg = 1, .val = 'p'},
            {.name = "ib-dev", .has_arg = 1, .val = 'd'},
            {.name = "ib-port", .has_arg = 1, .val = 'i'},
            {.name = "gid-idx", .has_arg = 1, .val = 'g'},
            {.name = "help", .has_arg = 0, .val = 'h'},
            {.name = NULL, .has_arg = 0, .val = '\0'}};
        // if a character is followed by a colon, the option is expected to have an argument,
        // which should be separated from it by white space.
        c = getopt_long(argc, argv, "p:d:i:g:h", long_options, NULL);
        if (c == -1)
            break;
        switch (c)
        {
        case 'p':
            config.tcp_port = strtoul(optarg, NULL, 0);
            break;
        case 'd':
            config.dev_name = strdup(optarg);
            break;
        case 'i':
            config.ib_port = strtoul(optarg, NULL, 0);
            if (config.ib_port < 0)
            {
                usage(argv[0]);
                return 1;
            }
            break;
        case 'g':
            config.gid_idx = strtoul(optarg, NULL, 0);
            if (config.gid_idx < 0)
            {
                usage(argv[0]);
                return 1;
            }
            break;
        case 'h':
        default:
            usage(argv[0]);
            return 1;
        }
    }
    /* parse the last parameter (if exists) as the server name */
    // optind is modified to index the first nonoption.
    // https://stackoverflow.com/questions/46636641/how-does-optind-get-assigned-in-c
    if (optind == argc - 1)
        config.server_name = argv[optind];
    else if (optind < argc)
    {
        usage(argv[0]);
        return 1;
    }
    /* print the used parameters for info*/
    print_config();
    /* init all of the resources, so cleanup will be easy */
    resources_init(&res);
    /* create resources before using them */
    if (resources_create(&res))
    {
        fprintf(stderr, "failed to create resources\n");
        goto main_exit;
    }
    /* connect the QPs */
    if (connect_qp(&res))
    {
        fprintf(stderr, "failed to connect QPs\n");
        goto main_exit;
    }
    /* let the server post the sr */
    if (!config.server_name)
        if (post_send(&res, IBV_WR_SEND))
        {
            fprintf(stderr, "failed to post sr\n");
            goto main_exit;
        }
    /* in both sides we expect to get a completion */
    if (poll_completion(&res))
    {
        fprintf(stderr, "poll completion failed\n");
        goto main_exit;
    }
    /* after polling the completion we have the message in the client buffer
    too */
    /* if client side */
    if (config.server_name)
    {
        fprintf(stdout, "Message is: '%s'\n", res.buf);
    }
    else
    {
        /* setup server buffer with read message */
        strcpy(res.buf, RDMAMSGR);
    }
    /* Sync so we are sure server side has data ready before client tries to
    read it */
    if (sock_sync_data(res.sock, 1, "R", &temp_char)) /* just send a dummy
    char back and forth */
    {
        fprintf(stderr, "sync error before RDMA ops\n");
        rc = 1;
        goto main_exit;
    }
    /* Now the client performs an RDMA read and then write on server.
    Note that the server has no idea these events have occured */
    if (config.server_name)
    {
        /* First we read contens of server's buffer */
        if (post_send(&res, IBV_WR_RDMA_READ))
        {
            fprintf(stderr, "failed to post SR 2\n");
            rc = 1;
            goto main_exit;
        }
        if (poll_completion(&res))
        {
            fprintf(stderr, "poll completion failed 2\n");
            rc = 1;
            goto main_exit;
        }
        fprintf(stdout, "Contents of server's buffer: '%s'\n", res.buf);
        /* Now we replace what's in the server's buffer */
        strcpy(res.buf, RDMAMSGW);
        fprintf(stdout, "Now replacing it with: '%s'\n", res.buf);
        if (post_send(&res, IBV_WR_RDMA_WRITE))
        {
            fprintf(stderr, "failed to post SR 3\n");
            rc = 1;
            goto main_exit;
        }
        if (poll_completion(&res))
        {
            fprintf(stderr, "poll completion failed 3\n");
            rc = 1;
            goto main_exit;
        }
    }
    /* Sync so server will know that client is done mucking with its memory */
    if (sock_sync_data(res.sock, 1, "W", &temp_char)) /* just send a dummy
    char back and forth */
    {
        fprintf(stderr, "sync error after RDMA ops\n");
        rc = 1;
        goto main_exit;
    }
    if (!config.server_name)
        fprintf(stdout, "Contents of server buffer: '%s'\n", res.buf);
    rc = 0;
main_exit:
    if (resources_destroy(&res))
    {
        fprintf(stderr, "failed to destroy resources\n");
        rc = 1;
    }
    if (config.dev_name)
        free((char *)config.dev_name);
    fprintf(stdout, "\ntest result is %d\n", rc);
    return rc;
}
运行演示

启动服务端
```
./RDMA_RC_example
```
启动客户端
```
./RDMA_RC_example localhost
```
运行结果

服务端输出示例

server output (show/hide)

客户端输出示例

client output (show/hide)