Re: [Qemu-devel] [PATCH v2 01/22] contrib/rdmacm-mux: Add implementation of RDMA User MAD multiplexer

[Yuval Shaia <yuval.shaia@oracle.com>]

On Sat, Nov 10, 2018 at 10:10:04PM +0200, Shamir Rabinovitch wrote:
> On Thu, Nov 08, 2018 at 06:07:57PM +0200, Yuval Shaia wrote:
> > RDMA MAD kernel module (ibcm) disallow more than one MAD-agent for a
> > given MAD class.
> > This does not go hand-by-hand with qemu pvrdma device's requirements
> > where each VM is MAD agent.
> > Fix it by adding implementation of RDMA MAD multiplexer service which on
> > one hand register as a sole MAD agent with the kernel module and on the
> > other hand gives service to more than one VM.
> > 
> > Design Overview:
> > ----------------
> > A server process is registered to UMAD framework (for this to work the
> > rdma_cm kernel module needs to be unloaded) and creates a unix socket to
> > listen to incoming request from clients.
> > A client process (such as QEMU) connects to this unix socket and
> > registers with its own GID.
> > 
> > TX:
> > ---
> > When client needs to send rdma_cm MAD message it construct it the same
> > way as without this multiplexer, i.e. creates a umad packet but this
> > time it writes its content to the socket instead of calling umad_send().
> > The server, upon receiving such a message fetch local_comm_id from it so
> > a context for this session can be maintain and relay the message to UMAD
> > layer by calling umad_send().
> > 
> > RX:
> > ---
> > The server creates a worker thread to process incoming rdma_cm MAD
> > messages. When an incoming message arrived (umad_recv()) the server,
> > depending on the message type (attr_id) looks for target client by
> > either searching in gid->fd table or in local_comm_id->fd table. With
> > the extracted fd the server relays to incoming message to the client.
> > 
> > Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
> > ---
> >  MAINTAINERS                      |   1 +
> >  Makefile                         |   3 +
> >  Makefile.objs                    |   1 +
> >  contrib/rdmacm-mux/Makefile.objs |   4 +
> >  contrib/rdmacm-mux/main.c        | 770 +++++++++++++++++++++++++++++++
> >  contrib/rdmacm-mux/rdmacm-mux.h  |  56 +++
> >  6 files changed, 835 insertions(+)
> >  create mode 100644 contrib/rdmacm-mux/Makefile.objs
> >  create mode 100644 contrib/rdmacm-mux/main.c
> >  create mode 100644 contrib/rdmacm-mux/rdmacm-mux.h
> > 
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 98a1856afc..e087d58ac6 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -2231,6 +2231,7 @@ S: Maintained
> >  F: hw/rdma/*
> >  F: hw/rdma/vmw/*
> >  F: docs/pvrdma.txt
> > +F: contrib/rdmacm-mux/*
> >  
> >  Build and test automation
> >  -------------------------
> > diff --git a/Makefile b/Makefile
> > index f2947186a4..94072776ff 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -418,6 +418,7 @@ dummy := $(call unnest-vars,, \
> >                  elf2dmp-obj-y \
> >                  ivshmem-client-obj-y \
> >                  ivshmem-server-obj-y \
> > +                rdmacm-mux-obj-y \
> >                  libvhost-user-obj-y \
> >                  vhost-user-scsi-obj-y \
> >                  vhost-user-blk-obj-y \
> > @@ -725,6 +726,8 @@ vhost-user-scsi$(EXESUF): $(vhost-user-scsi-obj-y) libvhost-user.a
> >  	$(call LINK, $^)
> >  vhost-user-blk$(EXESUF): $(vhost-user-blk-obj-y) libvhost-user.a
> >  	$(call LINK, $^)
> > +rdmacm-mux$(EXESUF): $(rdmacm-mux-obj-y) $(COMMON_LDADDS)
> > +	$(call LINK, $^)
> >  
> >  module_block.h: $(SRC_PATH)/scripts/modules/module_block.py config-host.mak
> >  	$(call quiet-command,$(PYTHON) $< $@ \
> > diff --git a/Makefile.objs b/Makefile.objs
> > index 1e1ff387d7..cc7df3ad80 100644
> > --- a/Makefile.objs
> > +++ b/Makefile.objs
> > @@ -194,6 +194,7 @@ vhost-user-scsi.o-cflags := $(LIBISCSI_CFLAGS)
> >  vhost-user-scsi.o-libs := $(LIBISCSI_LIBS)
> >  vhost-user-scsi-obj-y = contrib/vhost-user-scsi/
> >  vhost-user-blk-obj-y = contrib/vhost-user-blk/
> > +rdmacm-mux-obj-y = contrib/rdmacm-mux/
> >  
> >  ######################################################################
> >  trace-events-subdirs =
> > diff --git a/contrib/rdmacm-mux/Makefile.objs b/contrib/rdmacm-mux/Makefile.objs
> > new file mode 100644
> > index 0000000000..be3eacb6f7
> > --- /dev/null
> > +++ b/contrib/rdmacm-mux/Makefile.objs
> > @@ -0,0 +1,4 @@
> > +ifdef CONFIG_PVRDMA
> > +CFLAGS += -libumad -Wno-format-truncation
> > +rdmacm-mux-obj-y = main.o
> > +endif
> > diff --git a/contrib/rdmacm-mux/main.c b/contrib/rdmacm-mux/main.c
> > new file mode 100644
> > index 0000000000..0308074b15
> > --- /dev/null
> > +++ b/contrib/rdmacm-mux/main.c
> > @@ -0,0 +1,770 @@
> > +/*
> > + * QEMU paravirtual RDMA - rdmacm-mux implementation
> > + *
> > + * Copyright (C) 2018 Oracle
> > + * Copyright (C) 2018 Red Hat Inc
> > + *
> > + * Authors:
> > + *     Yuval Shaia <yuval.shaia@oracle.com>
> > + *     Marcel Apfelbaum <marcel@redhat.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> > + * See the COPYING file in the top-level directory.
> > + *
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +#include "sys/poll.h"
> > +#include "sys/ioctl.h"
> > +#include "pthread.h"
> > +#include "syslog.h"
> > +
> > +#include "infiniband/verbs.h"
> > +#include "infiniband/umad.h"
> > +#include "infiniband/umad_types.h"
> > +#include "infiniband/umad_sa.h"
> > +#include "infiniband/umad_cm.h"
> > +
> > +#include "rdmacm-mux.h"
> > +
> > +#define SCALE_US 1000
> > +#define COMMID_TTL 2 /* How many SCALE_US a context of MAD session is saved */
> > +#define SLEEP_SECS 5 /* This is used both in poll() and thread */
> > +#define SERVER_LISTEN_BACKLOG 10
> > +#define MAX_CLIENTS 4096
> > +#define MAD_RMPP_VERSION 0
> > +#define MAD_METHOD_MASK0 0x8
> > +
> > +#define IB_USER_MAD_LONGS_PER_METHOD_MASK (128 / (8 * sizeof(long)))
> > +
> > +#define CM_REQ_DGID_POS      80
> > +#define CM_SIDR_REQ_DGID_POS 44
> > +
> > +/* The below can be override by command line parameter */
> > +#define UNIX_SOCKET_PATH "/var/run/rdmacm-mux"
> > +#define RDMA_DEVICE "rxe0"
> > +#define RDMA_PORT_NUM 1
> > +
> > +typedef struct RdmaCmServerArgs {
> > +    char unix_socket_path[PATH_MAX];
> > +    char rdma_dev_name[NAME_MAX];
> > +    int rdma_port_num;
> > +} RdmaCMServerArgs;
> > +
> > +typedef struct CommId2FdEntry {
> > +    int fd;
> > +    int ttl; /* Initialized to 2, decrement each timeout, entry delete when 0 */
> > +    __be64 gid_ifid;
> > +} CommId2FdEntry;
> > +
> > +typedef struct RdmaCmUMadAgent {
> > +    int port_id;
> > +    int agent_id;
> > +    GHashTable *gid2fd; /* Used to find fd of a given gid */
> > +    GHashTable *commid2fd; /* Used to find fd on of a given comm_id */
> > +} RdmaCmUMadAgent;
> > +
> > +typedef struct RdmaCmServer {
> > +    bool run;
> > +    RdmaCMServerArgs args;
> > +    struct pollfd fds[MAX_CLIENTS];
> > +    int nfds;
> > +    RdmaCmUMadAgent umad_agent;
> > +    pthread_t umad_recv_thread;
> > +    pthread_rwlock_t lock;
> > +} RdmaCMServer;
> > +
> > +RdmaCMServer server = {0};
> 
> Maybe static is better here ?

Done.

> 
> > +
> > +static void usage(const char *progname)
> > +{
> > +    printf("Usage: %s [OPTION]...\n"
> > +           "Start a RDMA-CM multiplexer\n"
> > +           "\n"
> > +           "\t-h                    Show this help\n"
> > +           "\t-s unix-socket-path   Path to unix socket to listen on (default %s)\n"
> > +           "\t-d rdma-device-name   Name of RDMA device to register with (default %s)\n"
> > +           "\t-p rdma-device-port   Port number of RDMA device to register with (default %d)\n",
> > +           progname, UNIX_SOCKET_PATH, RDMA_DEVICE, RDMA_PORT_NUM);
> > +}
> > +
> > +static void help(const char *progname)
> > +{
> > +    fprintf(stderr, "Try '%s -h' for more information.\n", progname);
> > +}
> > +
> > +static void parse_args(int argc, char *argv[])
> > +{
> > +    int c;
> > +    char unix_socket_path[PATH_MAX];
> > +
> > +    strcpy(unix_socket_path, UNIX_SOCKET_PATH);
> > +    strncpy(server.args.rdma_dev_name, RDMA_DEVICE, NAME_MAX - 1);
> > +    server.args.rdma_port_num = RDMA_PORT_NUM;
> > +
> > +    while ((c = getopt(argc, argv, "hs:d:p:")) != -1) {
> > +        switch (c) {
> > +        case 'h':
> > +            usage(argv[0]);
> > +            exit(0);
> > +
> > +        case 's':
> > +            /* This is temporary, final name will build below */
> > +            strncpy(unix_socket_path, optarg, PATH_MAX);
> > +            break;
> > +
> > +        case 'd':
> > +            strncpy(server.args.rdma_dev_name, optarg, NAME_MAX - 1);
> > +            break;
> > +
> > +        case 'p':
> > +            server.args.rdma_port_num = atoi(optarg);
> > +            break;
> > +
> > +        default:
> > +            help(argv[0]);
> > +            exit(1);
> > +        }
> > +    }
> > +
> > +    /* Build unique unix-socket file name */
> > +    snprintf(server.args.unix_socket_path, PATH_MAX, "%s-%s-%d",
> > +             unix_socket_path, server.args.rdma_dev_name,
> > +             server.args.rdma_port_num);
> 
> Please check for truncation:
> "a return value of size or more means that the output was truncated"

So, you are suggesting to give a warning to a user that chooses a name with
more than 4096 characters, right?
Give a warning and then what? exit?
How about just truncating it, printing a log message [1] with the truncated
(corrected) name and continue as usual?

> 
> > +
> > +    syslog(LOG_INFO, "unix_socket_path=%s", server.args.unix_socket_path);

[1]
Log message here shows the final name anyway.

> > +    syslog(LOG_INFO, "rdma-device-name=%s", server.args.rdma_dev_name);
> > +    syslog(LOG_INFO, "rdma-device-port=%d", server.args.rdma_port_num);
> > +}
> > +
> > +static void hash_tbl_alloc(void)
> > +{
> > +
> > +    server.umad_agent.gid2fd = g_hash_table_new_full(g_int64_hash,
> > +                                                     g_int64_equal,
> > +                                                     g_free, g_free);
> > +    server.umad_agent.commid2fd = g_hash_table_new_full(g_int_hash,
> > +                                                        g_int_equal,
> > +                                                        g_free, g_free);
> 
> Any reason not to use 'g_hash_table_new' above ?

Just so i can use the cleaners? I'm not sure that they will be called just
because i'm using a primitives, it is not documented so can't trust it.

> 
> Can the above functions fail to create new hash table ? If yes, please
> add return status from this function and check it in the caller...

It can't.

> 
> > +}
> > +
> > +static void hash_tbl_free(void)
> > +{
> > +    if (server.umad_agent.commid2fd) {
> > +        g_hash_table_destroy(server.umad_agent.commid2fd);
> > +    }
> > +    if (server.umad_agent.gid2fd) {
> > +        g_hash_table_destroy(server.umad_agent.gid2fd);
> > +    }
> > +}
> > +
> > +
> > +static int _hash_tbl_search_fd_by_ifid(__be64 *gid_ifid)
> > +{
> > +    int *fd;
> > +
> > +    fd = g_hash_table_lookup(server.umad_agent.gid2fd, gid_ifid);
> > +    if (!fd) {
> > +        /* Let's try IPv4 */
> > +        *gid_ifid |= 0x00000000ffff0000;
> > +        fd = g_hash_table_lookup(server.umad_agent.gid2fd, gid_ifid);
> > +    }
> > +
> > +    return fd ? *fd : 0;
> > +}
> > +
> > +static int hash_tbl_search_fd_by_ifid(int *fd, __be64 *gid_ifid)
> > +{
> > +    pthread_rwlock_rdlock(&server.lock);
> > +    *fd = _hash_tbl_search_fd_by_ifid(gid_ifid);
> > +    pthread_rwlock_unlock(&server.lock);
> > +
> > +    if (!fd) {
> > +        syslog(LOG_WARNING, "Can't find matching for ifid 0x%llx\n", *gid_ifid);
> > +        return -ENOENT;
> > +    }
> > +
> > +    return 0;
> > +}
> > +
> > +static int hash_tbl_search_fd_by_comm_id(uint32_t comm_id, int *fd,
> > +                                         __be64 *gid_idid)
> > +{
> > +    CommId2FdEntry *fde;
> > +
> > +    pthread_rwlock_rdlock(&server.lock);
> > +    fde = g_hash_table_lookup(server.umad_agent.commid2fd, &comm_id);
> > +    pthread_rwlock_unlock(&server.lock);
> > +
> > +    if (!fde) {
> > +        syslog(LOG_WARNING, "Can't find matching for comm_id 0x%x\n", comm_id);
> > +        return -ENOENT;
> > +    }
> > +
> > +    *fd = fde->fd;
> > +    *gid_idid = fde->gid_ifid;
> > +
> > +    return 0;
> > +}
> > +
> > +static RdmaCmMuxErrCode add_fd_ifid_pair(int fd, __be64 gid_ifid)
> > +{
> > +    int fd1;
> > +
> > +    pthread_rwlock_wrlock(&server.lock);
> > +
> > +    fd1 = _hash_tbl_search_fd_by_ifid(&gid_ifid);
> > +    if (fd1) { /* record already exist - an error */
> > +        pthread_rwlock_unlock(&server.lock);
> > +        return fd == fd1 ? RDMACM_MUX_ERR_CODE_EEXIST :
> > +                           RDMACM_MUX_ERR_CODE_EACCES;
> > +    }
> > +
> > +    g_hash_table_insert(server.umad_agent.gid2fd, g_memdup(&gid_ifid,
> > +                        sizeof(gid_ifid)), g_memdup(&fd, sizeof(fd)));
> > +
> > +    pthread_rwlock_unlock(&server.lock);
> > +
> > +    syslog(LOG_INFO, "0x%lx registered on socket %d", (uint64_t)gid_ifid, fd);
> > +
> > +    return RDMACM_MUX_ERR_CODE_OK;
> > +}
> > +
> > +static RdmaCmMuxErrCode delete_fd_ifid_pair(int fd, __be64 gid_ifid)
> > +{
> > +    int fd1;
> > +
> > +    pthread_rwlock_wrlock(&server.lock);
> > +
> > +    fd1 = _hash_tbl_search_fd_by_ifid(&gid_ifid);
> > +    if (!fd1) { /* record not exist - an error */
> > +        pthread_rwlock_unlock(&server.lock);
> > +        return RDMACM_MUX_ERR_CODE_ENOTFOUND;
> > +    }
> > +
> > +    g_hash_table_remove(server.umad_agent.gid2fd, g_memdup(&gid_ifid,
> > +                        sizeof(gid_ifid)));
> > +    pthread_rwlock_unlock(&server.lock);
> > +
> > +    syslog(LOG_INFO, "0x%lx unregistered on socket %d", (uint64_t)gid_ifid, fd);
> > +
> > +    return RDMACM_MUX_ERR_CODE_OK;
> > +}
> > +
> > +static void hash_tbl_save_fd_comm_id_pair(int fd, uint32_t comm_id,
> > +                                          uint64_t gid_ifid)
> > +{
> > +    CommId2FdEntry fde = {fd, COMMID_TTL, gid_ifid};
> > +
> > +    pthread_rwlock_wrlock(&server.lock);
> > +    g_hash_table_insert(server.umad_agent.commid2fd,
> > +                        g_memdup(&comm_id, sizeof(comm_id)),
> > +                        g_memdup(&fde, sizeof(fde)));
> > +    pthread_rwlock_unlock(&server.lock);
> > +}
> > +
> > +static gboolean remove_old_comm_ids(gpointer key, gpointer value,
> > +                                    gpointer user_data)
> > +{
> > +    CommId2FdEntry *fde = (CommId2FdEntry *)value;
> > +
> > +    return !fde->ttl--;
> > +}
> > +
> > +static gboolean remove_entry_from_gid2fd(gpointer key, gpointer value,
> > +                                         gpointer user_data)
> > +{
> > +    if (*(int *)value == *(int *)user_data) {
> > +        syslog(LOG_INFO, "0x%lx unregistered on socket %d", *(uint64_t *)key,
> > +               *(int *)value);
> > +        return true;
> > +    }
> > +
> > +    return false;
> > +}
> > +
> > +static void hash_tbl_remove_fd_ifid_pair(int fd)
> > +{
> > +    pthread_rwlock_wrlock(&server.lock);
> > +    g_hash_table_foreach_remove(server.umad_agent.gid2fd,
> > +                                remove_entry_from_gid2fd, (gpointer)&fd);
> > +    pthread_rwlock_unlock(&server.lock);
> > +}
> > +
> > +static int get_fd(const char *mad, int *fd, __be64 *gid_ifid)
> > +{
> > +    struct umad_hdr *hdr = (struct umad_hdr *)mad;
> > +    char *data = (char *)hdr + sizeof(*hdr);
> > +    int32_t comm_id;
> > +    uint16_t attr_id = be16toh(hdr->attr_id);
> > +    int rc = 0;
> > +
> > +    switch (attr_id) {
> > +    case UMAD_CM_ATTR_REQ:
> > +        memcpy(gid_ifid, data + CM_REQ_DGID_POS, sizeof(*gid_ifid));
> > +        rc = hash_tbl_search_fd_by_ifid(fd, gid_ifid);
> > +        break;
> > +
> > +    case UMAD_CM_ATTR_SIDR_REQ:
> > +        memcpy(gid_ifid, data + CM_SIDR_REQ_DGID_POS, sizeof(*gid_ifid));
> > +        rc = hash_tbl_search_fd_by_ifid(fd, gid_ifid);
> > +        break;
> > +
> > +    case UMAD_CM_ATTR_REP:
> > +        /* Fall through */
> > +    case UMAD_CM_ATTR_REJ:
> > +        /* Fall through */
> > +    case UMAD_CM_ATTR_DREQ:
> > +        /* Fall through */
> > +    case UMAD_CM_ATTR_DREP:
> > +        /* Fall through */
> > +    case UMAD_CM_ATTR_RTU:
> > +        data += sizeof(comm_id);
> > +        /* Fall through */
> > +    case UMAD_CM_ATTR_SIDR_REP:
> > +        memcpy(&comm_id, data, sizeof(comm_id));
> > +        if (comm_id) {
> > +            rc = hash_tbl_search_fd_by_comm_id(comm_id, fd, gid_ifid);
> > +        }
> > +        break;
> > +
> > +    default:
> > +        rc = -EINVAL;
> > +        syslog(LOG_WARNING, "Unsupported attr_id 0x%x\n", attr_id);
> > +    }
> > +
> > +    return rc;
> > +}
> > +
> > +static void *umad_recv_thread_func(void *args)
> > +{
> > +    int rc;
> > +    RdmaCmMuxMsg msg = {0};
> > +    int fd = -2;
> > +
> > +    while (server.run) {
> > +        do {
> > +            msg.umad_len = sizeof(msg.umad.mad);
> > +            rc = umad_recv(server.umad_agent.port_id, &msg.umad, &msg.umad_len,
> > +                           SLEEP_SECS * SCALE_US);
> > +            if ((rc == -EIO) || (rc == -EINVAL)) {
> > +                syslog(LOG_CRIT, "Fatal error while trying to read MAD");
> > +            }
> > +
> > +            if (rc == -ETIMEDOUT) {
> > +                g_hash_table_foreach_remove(server.umad_agent.commid2fd,
> > +                                            remove_old_comm_ids, NULL);
> > +            }
> > +        } while (rc && server.run);
> > +
> > +        if (server.run) {
> > +            rc = get_fd(msg.umad.mad, &fd, &msg.hdr.sgid.global.interface_id);
> > +            if (rc) {
> > +                continue;
> > +            }
> > +
> > +            send(fd, &msg, sizeof(msg), 0);
> > +        }
> > +    }
> > +
> > +    return NULL;
> > +}
> > +
> > +static int read_and_process(int fd)
> > +{
> > +    int rc;
> > +    RdmaCmMuxMsg msg = {0};
> > +    struct umad_hdr *hdr;
> > +    uint32_t *comm_id;
> > +    uint16_t attr_id;
> > +
> > +    rc = recv(fd, &msg, sizeof(msg), 0);
> > +
> > +    if (rc < 0 && errno != EWOULDBLOCK) {
> > +        return -EIO;
> > +    }
> > +
> > +    if (!rc) {
> > +        return -EPIPE;
> > +    }
> > +
> > +    switch (msg.hdr.msg_type) {
> > +    case RDMACM_MUX_MSG_TYPE_REG:
> > +        rc = add_fd_ifid_pair(fd, msg.hdr.sgid.global.interface_id);
> > +        break;
> > +
> > +    case RDMACM_MUX_MSG_TYPE_UNREG:
> > +        rc = delete_fd_ifid_pair(fd, msg.hdr.sgid.global.interface_id);
> > +        break;
> > +
> > +    case RDMACM_MUX_MSG_TYPE_MAD:
> > +        /* If this is REQ or REP then store the pair comm_id,fd to be later
> > +         * used for other messages where gid is unknown */
> > +        hdr = (struct umad_hdr *)msg.umad.mad;
> > +        attr_id = be16toh(hdr->attr_id);
> > +        if ((attr_id == UMAD_CM_ATTR_REQ) || (attr_id == UMAD_CM_ATTR_DREQ) ||
> > +            (attr_id == UMAD_CM_ATTR_SIDR_REQ) ||
> > +            (attr_id == UMAD_CM_ATTR_REP) || (attr_id == UMAD_CM_ATTR_DREP)) {
> > +            comm_id = (uint32_t *)(msg.umad.mad + sizeof(*hdr));
> > +            hash_tbl_save_fd_comm_id_pair(fd, *comm_id,
> > +                                          msg.hdr.sgid.global.interface_id);
> > +        }
> > +
> > +        rc = umad_send(server.umad_agent.port_id, server.umad_agent.agent_id,
> > +                       &msg.umad, msg.umad_len, 1, 0);
> > +        if (rc) {
> > +            syslog(LOG_WARNING, "Fail to send MAD message, err=%d", rc);
> > +        }
> > +        break;
> > +
> > +    default:
> > +        syslog(LOG_WARNING, "Got invalid message (%d) from %d",
> > +               msg.hdr.msg_type, fd);
> > +        rc = RDMACM_MUX_ERR_CODE_EINVAL;
> > +    }
> > +
> > +    msg.hdr.msg_type = RDMACM_MUX_MSG_TYPE_RESP;
> > +    msg.hdr.err_code = rc;
> > +    rc = send(fd, &msg, sizeof(msg), 0);
> > +
> > +    return rc == sizeof(msg) ? 0 : -EPIPE;
> > +}
> > +
> > +static int accept_all(void)
> > +{
> > +    int fd, rc = 0;;
> > +
> > +    pthread_rwlock_wrlock(&server.lock);
> > +
> > +    do {
> > +        if ((server.nfds + 1) > MAX_CLIENTS) {
> > +            syslog(LOG_WARNING, "Too many clients (%d)", server.nfds);
> > +            rc = -EIO;
> > +            goto out;
> > +        }
> > +
> > +        fd = accept(server.fds[0].fd, NULL, NULL);
> > +        if (fd < 0) {
> > +            if (errno != EWOULDBLOCK) {
> > +                syslog(LOG_WARNING, "accept() failed");
> > +                rc = -EIO;
> > +                goto out;
> > +            }
> > +            break;
> > +        }
> > +
> > +        syslog(LOG_INFO, "Client connected on socket %d\n", fd);
> > +        server.fds[server.nfds].fd = fd;
> > +        server.fds[server.nfds].events = POLLIN;
> > +        server.nfds++;
> > +    } while (fd != -1);
> > +
> > +out:
> > +    pthread_rwlock_unlock(&server.lock);
> > +    return rc;
> > +}
> > +
> > +static void compress_fds(void)
> > +{
> > +    int i, j;
> > +    int closed = 0;
> > +
> > +    pthread_rwlock_wrlock(&server.lock);
> > +
> > +    for (i = 1; i < server.nfds; i++) {
> > +        if (!server.fds[i].fd) {
> > +            closed++;
> > +            for (j = i; j < server.nfds; j++) {
> > +                server.fds[j].fd = server.fds[j + 1].fd;
> > +            }
> > +        }
> > +    }
> > +
> > +    server.nfds -= closed;
> > +
> > +    pthread_rwlock_unlock(&server.lock);
> > +}
> > +
> > +static void close_fd(int idx)
> > +{
> > +    close(server.fds[idx].fd);
> > +    syslog(LOG_INFO, "Socket %d closed\n", server.fds[idx].fd);
> > +    hash_tbl_remove_fd_ifid_pair(server.fds[idx].fd);
> > +    server.fds[idx].fd = 0;
> > +}
> > +
> > +static void run(void)
> > +{
> > +    int rc, nfds, i;
> > +    bool compress = false;
> > +
> > +    syslog(LOG_INFO, "Service started");
> > +
> > +    while (server.run) {
> > +        rc = poll(server.fds, server.nfds, SLEEP_SECS * SCALE_US);
> > +        if (rc < 0) {
> > +            if (errno != EINTR) {
> > +                syslog(LOG_WARNING, "poll() failed");
> > +            }
> > +            continue;
> > +        }
> > +
> > +        if (rc == 0) {
> > +            continue;
> > +        }
> > +
> > +        nfds = server.nfds;
> > +        for (i = 0; i < nfds; i++) {
> > +            if (server.fds[i].revents == 0) {
> > +                continue;
> > +            }
> > +
> > +            if (server.fds[i].revents != POLLIN) {
> > +                if (i == 0) {
> > +                    syslog(LOG_NOTICE, "Unexpected poll() event (0x%x)\n",
> > +                           server.fds[i].revents);
> > +                } else {
> > +                    close_fd(i);
> > +                    compress = true;
> > +                }
> > +                continue;
> > +            }
> > +
> > +            if (i == 0) {
> > +                rc = accept_all();
> > +                if (rc) {
> > +                    continue;
> > +                }
> > +            } else {
> > +                rc = read_and_process(server.fds[i].fd);
> > +                if (rc) {
> > +                    close_fd(i);
> > +                    compress = true;
> > +                }
> > +            }
> > +        }
> > +
> > +        if (compress) {
> > +            compress = false;
> > +            compress_fds();
> > +        }
> > +    }
> > +}
> > +
> > +static void fini_listener(void)
> > +{
> > +    int i;
> > +
> > +    if (server.fds[0].fd <= 0) {
> > +        return;
> > +    }
> > +
> > +    for (i = server.nfds - 1; i >= 0; i--) {
> > +        if (server.fds[i].fd) {
> > +            close(server.fds[i].fd);
> > +        }
> > +    }
> > +
> > +    unlink(server.args.unix_socket_path);
> > +}
> > +
> > +static void fini_umad(void)
> > +{
> > +    if (server.umad_agent.agent_id) {
> > +        umad_unregister(server.umad_agent.port_id, server.umad_agent.agent_id);
> > +    }
> > +
> > +    if (server.umad_agent.port_id) {
> > +        umad_close_port(server.umad_agent.port_id);
> > +    }
> > +
> > +    hash_tbl_free();
> > +}
> > +
> > +static void fini(void)
> > +{
> > +    if (server.umad_recv_thread) {
> > +        pthread_join(server.umad_recv_thread, NULL);
> 
> Can pthread_join be called (raced) from signal handler & main ?
> 
> The man say this:
> "If multiple threads simultaneously try to join with the same thread,
> the results are undefined."
> 
> What ensure that above will not happen ?

[2]
To be on the safe side i will move the code that installs the sig handler
to after init is done, this way there will be only one caller to fini().

> 
> > +        server.umad_recv_thread = 0;
> > +    }
> > +    fini_umad();
> > +    fini_listener();
> > +    pthread_rwlock_destroy(&server.lock);
> 
> Same above question goes to here.
> 
> The man say this:
> "Results are undefined if a read-write lock is used without first being
> initialized."

Done ([2]).

> 
> > +
> > +    syslog(LOG_INFO, "Service going down");
> > +}
> > +
> > +static int init_listener(void)
> > +{
> > +    struct sockaddr_un sun;
> > +    int rc, on = 1;
> > +
> > +    server.fds[0].fd = socket(AF_UNIX, SOCK_STREAM, 0);
> > +    if (server.fds[0].fd < 0) {
> > +        syslog(LOG_ALERT, "socket() failed");
> > +        return -EIO;
> > +    }
> 
> Since you work with full mad messages, won't it be better to use
> SOCK_DGRAM ? Is there any use for partial mad message ?

This socket is also used for registration messages, these are not MAD.
Registration message is a message where client (VM) identifies itself with
a GID.

> 
> From the man:
> "SOCK_DGRAM, for a datagram-oriented socket that preserves message boundaries"
> 
> > +
> > +    rc = setsockopt(server.fds[0].fd, SOL_SOCKET, SO_REUSEADDR, (char *)&on,
> > +                    sizeof(on));
> > +    if (rc < 0) {
> > +        syslog(LOG_ALERT, "setsockopt() failed");
> > +        rc = -EIO;
> > +        goto err;
> > +    }
> > +
> > +    rc = ioctl(server.fds[0].fd, FIONBIO, (char *)&on);
> > +    if (rc < 0) {
> > +        syslog(LOG_ALERT, "ioctl() failed");
> > +        rc = -EIO;
> > +        goto err;
> > +    }
> > +
> > +    if (strlen(server.args.unix_socket_path) >= sizeof(sun.sun_path)) {
> > +        syslog(LOG_ALERT,
> > +               "Invalid unix_socket_path, size must be less than %ld\n",
> > +               sizeof(sun.sun_path));
> > +        rc = -EINVAL;
> > +        goto err;
> > +    }
> > +
> > +    sun.sun_family = AF_UNIX;
> > +    rc = snprintf(sun.sun_path, sizeof(sun.sun_path), "%s",
> > +                  server.args.unix_socket_path);
> > +    if (rc < 0 || rc >= sizeof(sun.sun_path)) {
> > +        syslog(LOG_ALERT, "Could not copy unix socket path\n");
> > +        rc = -EINVAL;
> > +        goto err;
> > +    }
> > +
> > +    rc = bind(server.fds[0].fd, (struct sockaddr *)&sun, sizeof(sun));
> > +    if (rc < 0) {
> > +        syslog(LOG_ALERT, "bind() failed");
> > +        rc = -EIO;
> > +        goto err;
> > +    }
> > +
> > +    rc = listen(server.fds[0].fd, SERVER_LISTEN_BACKLOG);
> > +    if (rc < 0) {
> > +        syslog(LOG_ALERT, "listen() failed");
> > +        rc = -EIO;
> > +        goto err;
> > +    }
> > +
> > +    server.fds[0].events = POLLIN;
> > +    server.nfds = 1;
> > +    server.run = true;
> > +
> > +    return 0;
> > +
> > +err:
> > +    close(server.fds[0].fd);
> > +    return rc;
> > +}
> > +
> > +static int init_umad(void)
> > +{
> > +    long method_mask[IB_USER_MAD_LONGS_PER_METHOD_MASK];
> > +
> > +    server.umad_agent.port_id = umad_open_port(server.args.rdma_dev_name,
> > +                                               server.args.rdma_port_num);
> > +
> > +    if (server.umad_agent.port_id < 0) {
> > +        syslog(LOG_WARNING, "umad_open_port() failed");
> > +        return -EIO;
> > +    }
> > +
> > +    memset(&method_mask, 0, sizeof(method_mask));
> > +    method_mask[0] = MAD_METHOD_MASK0;
> > +    server.umad_agent.agent_id = umad_register(server.umad_agent.port_id,
> > +                                               UMAD_CLASS_CM,
> > +                                               UMAD_SA_CLASS_VERSION,
> > +                                               MAD_RMPP_VERSION, method_mask);
> > +    if (server.umad_agent.agent_id < 0) {
> > +        syslog(LOG_WARNING, "umad_register() failed");
> > +        return -EIO;
> > +    }
> > +
> > +    hash_tbl_alloc();
> > +
> > +    return 0;
> > +}
> > +
> > +static void signal_handler(int sig, siginfo_t *siginfo, void *context)
> > +{
> > +    static bool warned;
> > +
> > +    /* Prevent stop if clients are connected */
> > +    if (server.nfds != 1) {
> > +        if (!warned) {
> > +            syslog(LOG_WARNING,
> > +                   "Can't stop while active client exist, resend SIGINT to overid");
> > +            warned = true;
> > +            return;
> > +        }
> > +    }
> > +
> > +    if (sig == SIGINT) {
> > +        server.run = false;
> > +        fini();
> > +    }
> > +
> > +    exit(0);
> > +}
> > +
> > +static int init(void)
> > +{
> > +    int rc;
> > +
> > +    rc = init_listener();
> > +    if (rc) {
> > +        return rc;
> > +    }
> > +
> > +    rc = init_umad();
> > +    if (rc) {
> > +        return rc;
> > +    }
> > +
> > +    pthread_rwlock_init(&server.lock, 0);
> > +
> > +    rc = pthread_create(&server.umad_recv_thread, NULL, umad_recv_thread_func,
> > +                        NULL);
> > +    if (!rc) {
> > +        return rc;
> > +    }
> > +
> > +    return 0;
> > +}
> > +
> > +int main(int argc, char *argv[])
> > +{
> > +    int rc;
> > +    struct sigaction sig = {0};
> > +
> > +    sig.sa_sigaction = &signal_handler;
> > +    sig.sa_flags = SA_SIGINFO;
> > +
> > +    if (sigaction(SIGINT, &sig, NULL) < 0) {
> > +        syslog(LOG_ERR, "Fail to install SIGINT handler\n");
> > +        return -EAGAIN;
> > +    }
> > +
> > +    memset(&server, 0, sizeof(server));
> > +
> > +    parse_args(argc, argv);
> > +
> > +    rc = init();
> > +    if (rc) {
> > +        syslog(LOG_ERR, "Fail to initialize server (%d)\n", rc);
> > +        rc = -EAGAIN;
> > +        goto out;
> > +    }
> > +
> > +    run();
> > +
> > +out:
> > +    fini();
> > +
> > +    return rc;
> > +}
> > diff --git a/contrib/rdmacm-mux/rdmacm-mux.h b/contrib/rdmacm-mux/rdmacm-mux.h
> > new file mode 100644
> > index 0000000000..03508d52b2
> > --- /dev/null
> > +++ b/contrib/rdmacm-mux/rdmacm-mux.h
> > @@ -0,0 +1,56 @@
> > +/*
> > + * QEMU paravirtual RDMA - rdmacm-mux declarations
> > + *
> > + * Copyright (C) 2018 Oracle
> > + * Copyright (C) 2018 Red Hat Inc
> > + *
> > + * Authors:
> > + *     Yuval Shaia <yuval.shaia@oracle.com>
> > + *     Marcel Apfelbaum <marcel@redhat.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> > + * See the COPYING file in the top-level directory.
> > + *
> > + */
> > +
> > +#ifndef RDMACM_MUX_H
> > +#define RDMACM_MUX_H
> > +
> > +#include "linux/if.h"
> > +#include "infiniband/verbs.h"
> > +#include "infiniband/umad.h"
> > +#include "rdma/rdma_user_cm.h"
> > +
> > +typedef enum RdmaCmMuxMsgType {
> > +    RDMACM_MUX_MSG_TYPE_REG   = 0,
> > +    RDMACM_MUX_MSG_TYPE_UNREG = 1,
> > +    RDMACM_MUX_MSG_TYPE_MAD   = 2,
> > +    RDMACM_MUX_MSG_TYPE_RESP  = 3,
> > +} RdmaCmMuxMsgType;
> > +
> > +typedef enum RdmaCmMuxErrCode {
> > +    RDMACM_MUX_ERR_CODE_OK        = 0,
> > +    RDMACM_MUX_ERR_CODE_EINVAL    = 1,
> > +    RDMACM_MUX_ERR_CODE_EEXIST    = 2,
> > +    RDMACM_MUX_ERR_CODE_EACCES    = 3,
> > +    RDMACM_MUX_ERR_CODE_ENOTFOUND = 4,
> > +} RdmaCmMuxErrCode;
> > +
> > +typedef struct RdmaCmMuxHdr {
> > +    RdmaCmMuxMsgType msg_type;
> > +    union ibv_gid sgid;
> > +    RdmaCmMuxErrCode err_code;
> > +} RdmaCmUHdr;
> > +
> > +typedef struct RdmaCmUMad {
> > +    struct ib_user_mad hdr;
> > +    char mad[RDMA_MAX_PRIVATE_DATA];
> > +} RdmaCmUMad;
> > +
> > +typedef struct RdmaCmMuxMsg {
> > +    RdmaCmUHdr hdr;
> > +    int umad_len;
> > +    RdmaCmUMad umad;
> > +} RdmaCmMuxMsg;
> > +
> > +#endif
> > -- 
> > 2.17.2
> >