How to write a Hello World iWarp application?

Question

I am trying to write a small program demonstrating Remote DMA over iWarp. I have the softiwarp Linux kernel module loaded and the userspace library compiled.

I am looking for documentation or sample code that explains setting up a connection and, e.g., sending a simple data block to the remote end ("Hello World!") to get me started, yet all I can find is the OpenFabrics' training web site, which is not helpful at all.

Answer 1

#include <arpa/inet.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <getopt.h>
#include <stdlib.h>
#include <unistd.h>
#include <rdma/rdma_cma.h>

struct Args {
    char *remote_addr;
    int is_server;
    int port;
};

struct Args args;

int main(int argc, char *argv[])
{
    struct rdma_event_channel *evch;
    struct rdma_cm_id *server_id;
    struct rdma_cm_id *client_id;
    struct rdma_cm_event *event;
    struct rdma_conn_param conn_param;
    struct ibv_pd *pd;
    struct ibv_cq *cq;
    struct ibv_mr *mr;
    struct ibv_send_wr snd_wr;
    struct ibv_recv_wr rcv_wr;
    struct ibv_sge sge;
    struct ibv_wc wc;
    struct ibv_qp_init_attr attr = {
        .cap = {
            .max_send_wr = 32,
            .max_recv_wr = 32,
            .max_send_sge = 1,
            .max_recv_sge = 1,
            .max_inline_data = 64
        },
        .qp_type = IBV_QPT_RC
    };

    char msg[256] = "Hello World";
    int msg_len = strlen(msg) + 1;
    struct sockaddr_in sin;

    args.remote_addr = "0.0.0.0";
    args.is_server = 1;
    args.port = 21234;

    /* Parameter parsing. */
    while (1) {
        int c;

        c = getopt(argc, argv, "c:p:");
        if (c == -1)
            break;

        switch (c) {
        case 'c':
            args.is_server = 0;
            args.remote_addr = optarg;
            break;
        case 'p':
            args.port = strtol(optarg, NULL, 0);
            break;
        default:
            perror("Invalid option");
            exit(-1);
        };
    }

    if (args.is_server) {
        if (!(evch = rdma_create_event_channel())) {
            perror("rdma_create_event_channel");
            exit(-1);
        }

        if (rdma_create_id(evch, &server_id, NULL, RDMA_PS_TCP)) {
            perror("rdma_create_id");
            exit(-1);
        }

        sin.sin_family = AF_INET;
        sin.sin_port = htons(args.port);
        sin.sin_addr.s_addr = htonl(INADDR_ANY);

        if (rdma_bind_addr(server_id, (struct sockaddr *)&sin)) {
            perror("rdma_bind_addr");
            exit(-1);
        }

        if (rdma_listen(server_id, 6)) {
            perror("rdma_listen");
            exit(-1);
        }

        if (rdma_get_cm_event(evch, &event)
            || event->event != RDMA_CM_EVENT_CONNECT_REQUEST) {
            perror("rdma_get_cm_event");
            exit(-1);
        }

        client_id = (struct rdma_cm_id *)event->id;

        if (!(pd = ibv_alloc_pd(client_id->verbs))) {
            perror("ibv_alloc_pd");
            exit(-1);
        }

        if (!(mr = ibv_reg_mr(pd, msg, 256,
                IBV_ACCESS_REMOTE_WRITE |
                IBV_ACCESS_LOCAL_WRITE |
                IBV_ACCESS_REMOTE_READ))) {
            perror("ibv_reg_mr");
            exit(-1);
        }

        if (!(cq = ibv_create_cq(client_id->verbs, 32, 0, 0, 0))) {
            perror("ibv_create_cq");
            exit(-1);
        }

        attr.send_cq = attr.recv_cq = cq;
        if (rdma_create_qp(client_id, pd, &attr)) {
            perror("rdma_create_qp");
            exit(-1);
        }

        memset(&conn_param, 0, sizeof conn_param);
        if (rdma_accept(client_id, &conn_param)) {
            perror("rdma_accept");
            exit(-1);
        }

        rdma_ack_cm_event(event);
        if (rdma_get_cm_event(evch, &event)
            || event->event != RDMA_CM_EVENT_ESTABLISHED) {
            perror("rdma_get_cm_event");
            exit(-1);
        }
        rdma_ack_cm_event(event);

        sge.addr = (uint64_t)msg;
        sge.length = msg_len;
        sge.lkey = mr->lkey;
        snd_wr.sg_list = &sge;
        snd_wr.num_sge = 1;
        snd_wr.opcode = IBV_WR_SEND;
        snd_wr.send_flags = IBV_SEND_SIGNALED;
        snd_wr.next = NULL;
        if (ibv_post_send(client_id->qp, &snd_wr, NULL)) {
            perror("ibv_post_send");
            exit(-1);
        }

        while (!ibv_poll_cq(cq, 1, &wc))
            ;
        if (wc.status != IBV_WC_SUCCESS) {
            perror("ibv_poll_cq");
            exit(-1);
        }
    }

    else {
        if (!(evch = rdma_create_event_channel())) {
            perror("rdma_create_event_channel");
            exit(-1);
        }

        if (rdma_create_id(evch, &client_id, NULL, RDMA_PS_TCP)) {
            perror("rdma_create_id");
            exit(-1);
        }

        sin.sin_family = AF_INET;
        sin.sin_port = htons(args.port);
        sin.sin_addr.s_addr = inet_addr(args.remote_addr);

        if (rdma_resolve_addr
            (client_id, NULL, (struct sockaddr *)&sin, 2000)) {
            perror("rdma_resolve_addr");
            exit(-1);
        }

        if (rdma_get_cm_event(evch, &event)
            || event->event != RDMA_CM_EVENT_ADDR_RESOLVED) {
            perror("rdma_get_cm_event");
            exit(-1);
        }
        rdma_ack_cm_event(event);

        if (rdma_resolve_route(client_id, 2000)) {
            perror("rdma_resolve_route");
            exit(-1);
        }

        if (rdma_get_cm_event(evch, &event)
            || event->event != RDMA_CM_EVENT_ROUTE_RESOLVED) {
            perror("rdma_get_cm_event");
            exit(-1);
        }
        rdma_ack_cm_event(event);

        if (!(pd = ibv_alloc_pd(client_id->verbs))) {
            perror("ibv_alloc_pd");
            exit(-1);
        }

        if (!(mr = ibv_reg_mr(pd, msg, 256,
                IBV_ACCESS_REMOTE_WRITE |
                IBV_ACCESS_LOCAL_WRITE |
                IBV_ACCESS_REMOTE_READ))) {
            perror("ibv_reg_mr");
            exit(-1);
        }

        if (!(cq = ibv_create_cq(client_id->verbs, 32, 0, 0, 0))) {
            perror("ibv_create_cq");
            exit(-1);
        }

        attr.send_cq = attr.recv_cq = cq;
        if (rdma_create_qp(client_id, pd, &attr)) {
            perror("rdma_create_qp");
            exit(-1);
        }

        sge.addr = (uint64_t)msg;
        sge.length = msg_len;
        sge.lkey = mr->lkey;
        rcv_wr.sg_list = &sge;
        rcv_wr.num_sge = 1;
        rcv_wr.next = NULL;
        if (ibv_post_recv(client_id->qp, &rcv_wr, NULL)) {
            perror("ibv_post_recv");
            exit(-1);
        }

        memset(&conn_param, 0, sizeof conn_param);
        if (rdma_connect(client_id, &conn_param)) {
            perror("rdma_connect");
            exit(-1);
        }

        if (rdma_get_cm_event(evch, &event)
            || event->event != RDMA_CM_EVENT_ESTABLISHED) {
            perror("rdma_get_cm_event");
            exit(-1);
        }
        rdma_ack_cm_event(event);

        while (!ibv_poll_cq(cq, 1, &wc)) ;
        if (wc.status != IBV_WC_SUCCESS) {
            perror("ibv_poll_cq");
            exit(-1);
        }

        fprintf(stdout, "Received %s \n", msg);
    }

    fprintf(stdout, "Done \n");
    return 0;
}

Answer 2

Probably the best documentation and examples are in the librdmacm source. It includes full man pages around establishing connections (actually moving data is in the libibverbs man pages), as well as a number of example programs under the examples directory. The simplest example is rping.

As the comment says, trying to code something up and then asking specific questions is more productive.