Version 2.2.3
[lttng-ust.git] / liblttng-ust-comm / lttng-ust-comm.c
index f469567690b3a9a88a2d7f4252417e130a1c6975..751ad2e3cf2add1ffd805c9ca4df802034e793b1 100644 (file)
 #include <errno.h>
 #include <fcntl.h>
 
+#include <lttng/ust-ctl.h>
 #include <ust-comm.h>
 #include <helper.h>
 #include <lttng/ust-error.h>
+#include <lttng/ust-events.h>
+#include <usterr-signal-safe.h>
+
+#include "../liblttng-ust/compat.h"
 
 #define USTCOMM_CODE_OFFSET(code)      \
        (code == LTTNG_UST_OK ? 0 : (code - LTTNG_UST_ERR + 1))
@@ -52,6 +57,10 @@ static const char *ustcomm_readable_code[] = {
        [ USTCOMM_CODE_OFFSET(LTTNG_UST_ERR_PERM) ] = "Permission denied",
        [ USTCOMM_CODE_OFFSET(LTTNG_UST_ERR_NOSYS) ] = "Not implemented",
        [ USTCOMM_CODE_OFFSET(LTTNG_UST_ERR_EXITING) ] = "Process is exiting",
+
+       [ USTCOMM_CODE_OFFSET(LTTNG_UST_ERR_INVAL_MAGIC) ] = "Invalid magic number",
+       [ USTCOMM_CODE_OFFSET(LTTNG_UST_ERR_INVAL_SOCKET_TYPE) ] = "Invalid socket type",
+       [ USTCOMM_CODE_OFFSET(LTTNG_UST_ERR_UNSUP_MAJOR) ] = "Unsupported major version",
 };
 
 /*
@@ -70,7 +79,6 @@ const char *lttng_ust_strerror(int code)
        if (code >= LTTNG_UST_ERR_NR)
                code = LTTNG_UST_ERR;
        return ustcomm_readable_code[USTCOMM_CODE_OFFSET(code)];
-
 }
 
 /*
@@ -89,13 +97,13 @@ int ustcomm_connect_unix_sock(const char *pathname)
         */
        fd = socket(PF_UNIX, SOCK_STREAM, 0);
        if (fd < 0) {
-               perror("socket");
+               PERROR("socket");
                ret = -errno;
                goto error;
        }
        ret = fcntl(fd, F_SETFD, FD_CLOEXEC);
        if (ret < 0) {
-               perror("fcntl");
+               PERROR("fcntl");
                ret = -errno;
                goto error_fcntl;
        }
@@ -108,11 +116,18 @@ int ustcomm_connect_unix_sock(const char *pathname)
        ret = connect(fd, (struct sockaddr *) &sun, sizeof(sun));
        if (ret < 0) {
                /*
-                * Don't print message on connect error, because connect
-                * is used in normal execution to detect if sessiond is
-                * alive.
+                * Don't print message on connect ENOENT error, because
+                * connect is used in normal execution to detect if
+                * sessiond is alive. ENOENT is when the unix socket
+                * file does not exist, and ECONNREFUSED is when the
+                * file exists but no sessiond is listening.
                 */
+               if (errno != ECONNREFUSED && errno != ECONNRESET
+                               && errno != ENOENT && errno != EACCES)
+                       PERROR("connect");
                ret = -errno;
+               if (ret == -ECONNREFUSED || ret == -ECONNRESET)
+                       ret = -EPIPE;
                goto error_connect;
        }
 
@@ -125,7 +140,7 @@ error_fcntl:
 
                closeret = close(fd);
                if (closeret)
-                       perror("close");
+                       PERROR("close");
        }
 error:
        return ret;
@@ -146,8 +161,11 @@ int ustcomm_accept_unix_sock(int sock)
        /* Blocking call */
        new_fd = accept(sock, (struct sockaddr *) &sun, &len);
        if (new_fd < 0) {
-               perror("accept");
-               return -errno;
+               if (errno != ECONNABORTED)
+                       PERROR("accept");
+               new_fd = -errno;
+               if (new_fd == -ECONNABORTED)
+                       new_fd = -EPIPE;
        }
        return new_fd;
 }
@@ -165,7 +183,7 @@ int ustcomm_create_unix_sock(const char *pathname)
 
        /* Create server socket */
        if ((fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0) {
-               perror("socket");
+               PERROR("socket");
                ret = -errno;
                goto error;
        }
@@ -179,7 +197,7 @@ int ustcomm_create_unix_sock(const char *pathname)
        (void) unlink(pathname);
        ret = bind(fd, (struct sockaddr *) &sun, sizeof(sun));
        if (ret < 0) {
-               perror("bind");
+               PERROR("bind");
                ret = -errno;
                goto error_close;
        }
@@ -192,7 +210,7 @@ error_close:
 
                closeret = close(fd);
                if (closeret) {
-                       perror("close");
+                       PERROR("close");
                }
        }
 error:
@@ -211,7 +229,7 @@ int ustcomm_listen_unix_sock(int sock)
        ret = listen(sock, LTTNG_UST_COMM_MAX_LISTEN);
        if (ret < 0) {
                ret = -errno;
-               perror("listen");
+               PERROR("listen");
        }
 
        return ret;
@@ -228,7 +246,7 @@ int ustcomm_close_unix_sock(int sock)
 
        ret = close(sock);
        if (ret < 0) {
-               perror("close");
+               PERROR("close");
                ret = -errno;
        }
 
@@ -247,7 +265,8 @@ ssize_t ustcomm_recv_unix_sock(int sock, void *buf, size_t len)
 {
        struct msghdr msg;
        struct iovec iov[1];
-       ssize_t ret;
+       ssize_t ret = -1;
+       size_t len_last;
 
        memset(&msg, 0, sizeof(msg));
 
@@ -257,20 +276,31 @@ ssize_t ustcomm_recv_unix_sock(int sock, void *buf, size_t len)
        msg.msg_iovlen = 1;
 
        do {
+               len_last = iov[0].iov_len;
                ret = recvmsg(sock, &msg, 0);
-       } while (ret < 0 && errno == EINTR);
+               if (ret > 0) {
+                       iov[0].iov_base += ret;
+                       iov[0].iov_len -= ret;
+                       assert(ret <= len_last);
+               }
+       } while ((ret > 0 && ret < len_last) || (ret < 0 && errno == EINTR));
 
        if (ret < 0) {
                int shutret;
 
-               if (errno != EPIPE && errno != ECONNRESET)
-                       perror("recvmsg");
+               if (errno != EPIPE && errno != ECONNRESET && errno != ECONNREFUSED)
+                       PERROR("recvmsg");
                ret = -errno;
+               if (ret == -ECONNRESET || ret == -ECONNREFUSED)
+                       ret = -EPIPE;
 
                shutret = shutdown(sock, SHUT_RDWR);
                if (shutret)
-                       fprintf(stderr, "Socket shutdown error");
+                       ERR("Socket shutdown error");
+       } else if (ret > 0) {
+               ret = len;
        }
+       /* ret = 0 means an orderly shutdown. */
 
        return ret;
 }
@@ -281,7 +311,7 @@ ssize_t ustcomm_recv_unix_sock(int sock, void *buf, size_t len)
  * Send buf data of size len. Using sendmsg API.
  * Return the size of sent data.
  */
-ssize_t ustcomm_send_unix_sock(int sock, void *buf, size_t len)
+ssize_t ustcomm_send_unix_sock(int sock, const void *buf, size_t len)
 {
        struct msghdr msg;
        struct iovec iov[1];
@@ -289,7 +319,7 @@ ssize_t ustcomm_send_unix_sock(int sock, void *buf, size_t len)
 
        memset(&msg, 0, sizeof(msg));
 
-       iov[0].iov_base = buf;
+       iov[0].iov_base = (void *) buf;
        iov[0].iov_len = len;
        msg.msg_iov = iov;
        msg.msg_iovlen = 1;
@@ -309,12 +339,14 @@ ssize_t ustcomm_send_unix_sock(int sock, void *buf, size_t len)
                int shutret;
 
                if (errno != EPIPE && errno != ECONNRESET)
-                       perror("sendmsg");
+                       PERROR("sendmsg");
                ret = -errno;
+               if (ret == -ECONNRESET)
+                       ret = -EPIPE;
 
                shutret = shutdown(sock, SHUT_RDWR);
                if (shutret)
-                       fprintf(stderr, "Socket shutdown error");
+                       ERR("Socket shutdown error");
        }
 
        return ret;
@@ -365,8 +397,11 @@ ssize_t ustcomm_send_fds_unix_sock(int sock, int *fds, size_t nb_fd)
                 * We consider EPIPE and ECONNRESET as expected.
                 */
                if (errno != EPIPE && errno != ECONNRESET) {
-                       perror("sendmsg");
+                       PERROR("sendmsg");
                }
+               ret = -errno;
+               if (ret == -ECONNRESET)
+                       ret = -EPIPE;
        }
        return ret;
 }
@@ -405,10 +440,11 @@ ssize_t ustcomm_recv_fds_unix_sock(int sock, int *fds, size_t nb_fd)
        } while (ret < 0 && errno == EINTR);
        if (ret < 0) {
                if (errno != EPIPE && errno != ECONNRESET) {
-                       perror("recvmsg fds");
+                       PERROR("recvmsg fds");
                }
-               if (errno == EPIPE || errno == ECONNRESET)
-                       ret = -errno;
+               ret = -errno;
+               if (ret == -ECONNRESET)
+                       ret = -EPIPE;
                goto end;
        }
        if (ret == 0) {
@@ -417,28 +453,28 @@ ssize_t ustcomm_recv_fds_unix_sock(int sock, int *fds, size_t nb_fd)
                goto end;
        }
        if (ret != 1) {
-               fprintf(stderr, "Error: Received %zd bytes, expected %d\n",
+               ERR("Error: Received %zd bytes, expected %d\n",
                                ret, 1);
                goto end;
        }
        if (msg.msg_flags & MSG_CTRUNC) {
-               fprintf(stderr, "Error: Control message truncated.\n");
+               ERR("Error: Control message truncated.\n");
                ret = -1;
                goto end;
        }
        cmsg = CMSG_FIRSTHDR(&msg);
        if (!cmsg) {
-               fprintf(stderr, "Error: Invalid control message header\n");
+               ERR("Error: Invalid control message header\n");
                ret = -1;
                goto end;
        }
        if (cmsg->cmsg_level != SOL_SOCKET || cmsg->cmsg_type != SCM_RIGHTS) {
-               fprintf(stderr, "Didn't received any fd\n");
+               ERR("Didn't received any fd\n");
                ret = -1;
                goto end;
        }
        if (cmsg->cmsg_len != CMSG_LEN(sizeof_fds)) {
-               fprintf(stderr, "Error: Received %zu bytes of ancillary data, expected %zu\n",
+               ERR("Error: Received %zu bytes of ancillary data, expected %zu\n",
                                (size_t) cmsg->cmsg_len, (size_t) CMSG_LEN(sizeof_fds));
                ret = -1;
                goto end;
@@ -461,7 +497,7 @@ int ustcomm_send_app_msg(int sock, struct ustcomm_ust_msg *lum)
                if (len < 0) {
                        return len;
                } else {
-                       fprintf(stderr, "incorrect message size: %zd\n", len);
+                       ERR("incorrect message size: %zd\n", len);
                        return -EINVAL;
                }
        }
@@ -480,28 +516,23 @@ int ustcomm_recv_app_reply(int sock, struct ustcomm_ust_reply *lur,
                return -EPIPE;
        case sizeof(*lur):
                if (lur->handle != expected_handle) {
-                       fprintf(stderr, "Unexpected result message handle: "
+                       ERR("Unexpected result message handle: "
                                "expected: %u vs received: %u\n",
                                expected_handle, lur->handle);
                        return -EINVAL;
                }
                if (lur->cmd != expected_cmd) {
-                       fprintf(stderr, "Unexpected result message command "
+                       ERR("Unexpected result message command "
                                "expected: %u vs received: %u\n",
                                expected_cmd, lur->cmd);
                        return -EINVAL;
                }
                return lur->ret_code;
        default:
-               if (len < 0) {
-                       /* Transport level error */
-                       if (errno == EPIPE || errno == ECONNRESET)
-                               len = -errno;
-                       return len;
-               } else {
-                       fprintf(stderr, "incorrect message size: %zd\n", len);
-                       return len;
+               if (len >= 0) {
+                       ERR("incorrect message size: %zd\n", len);
                }
+               return len;
        }
 }
 
@@ -525,10 +556,12 @@ int ustcomm_send_app_cmd(int sock,
  * expected var_len.
  */
 ssize_t ustcomm_recv_channel_from_sessiond(int sock,
-               void **_chan_data, uint64_t var_len)
+               void **_chan_data, uint64_t var_len,
+               int *_wakeup_fd)
 {
        void *chan_data;
-       ssize_t len;
+       ssize_t len, nr_fd;
+       int wakeup_fd;
 
        if (var_len > LTTNG_UST_CHANNEL_DATA_MAX_LEN) {
                len = -EINVAL;
@@ -544,6 +577,18 @@ ssize_t ustcomm_recv_channel_from_sessiond(int sock,
        if (len != var_len) {
                goto error_recv;
        }
+       /* recv wakeup fd */
+       nr_fd = ustcomm_recv_fds_unix_sock(sock, &wakeup_fd, 1);
+       if (nr_fd <= 0) {
+               if (nr_fd < 0) {
+                       len = nr_fd;
+                       goto error_recv;
+               } else {
+                       len = -EIO;
+                       goto error_recv;
+               }
+       }
+       *_wakeup_fd = wakeup_fd;
        *_chan_data = chan_data;
        return len;
 
@@ -580,3 +625,537 @@ int ustcomm_recv_stream_from_sessiond(int sock,
 error:
        return ret;
 }
+
+/*
+ * Returns 0 on success, negative error value on error.
+ */
+int ustcomm_send_reg_msg(int sock,
+               enum ustctl_socket_type type,
+               uint32_t bits_per_long,
+               uint32_t uint8_t_alignment,
+               uint32_t uint16_t_alignment,
+               uint32_t uint32_t_alignment,
+               uint32_t uint64_t_alignment,
+               uint32_t long_alignment)
+{
+       ssize_t len;
+       struct ustctl_reg_msg reg_msg;
+
+       reg_msg.magic = LTTNG_UST_COMM_MAGIC;
+       reg_msg.major = LTTNG_UST_ABI_MAJOR_VERSION;
+       reg_msg.minor = LTTNG_UST_ABI_MINOR_VERSION;
+       reg_msg.pid = getpid();
+       reg_msg.ppid = getppid();
+       reg_msg.uid = getuid();
+       reg_msg.gid = getgid();
+       reg_msg.bits_per_long = bits_per_long;
+       reg_msg.uint8_t_alignment = uint8_t_alignment;
+       reg_msg.uint16_t_alignment = uint16_t_alignment;
+       reg_msg.uint32_t_alignment = uint32_t_alignment;
+       reg_msg.uint64_t_alignment = uint64_t_alignment;
+       reg_msg.long_alignment = long_alignment;
+       reg_msg.socket_type = type;
+       lttng_ust_getprocname(reg_msg.name);
+       memset(reg_msg.padding, 0, sizeof(reg_msg.padding));
+
+       len = ustcomm_send_unix_sock(sock, &reg_msg, sizeof(reg_msg));
+       if (len > 0 && len != sizeof(reg_msg))
+               return -EIO;
+       if (len < 0)
+               return len;
+       return 0;
+}
+
+static
+int serialize_string_encoding(enum ustctl_string_encodings *ue,
+               enum lttng_string_encodings le)
+{
+       switch (le) {
+       case lttng_encode_none:
+               *ue = ustctl_encode_none;
+               break;
+       case lttng_encode_UTF8:
+               *ue = ustctl_encode_UTF8;
+               break;
+       case lttng_encode_ASCII:
+               *ue = ustctl_encode_ASCII;
+               break;
+       default:
+               return -EINVAL;
+       }
+       return 0;
+}
+
+static
+int serialize_basic_type(enum ustctl_abstract_types *uatype,
+               enum lttng_abstract_types atype,
+               union _ustctl_basic_type *ubt,
+               const union _lttng_basic_type *lbt)
+{
+       switch (atype) {
+       case atype_integer:
+       {
+               struct ustctl_integer_type *uit;
+               const struct lttng_integer_type *lit;
+
+               uit = &ubt->integer;
+               lit = &lbt->integer;
+               uit->size = lit->size;
+               uit->signedness = lit->signedness;
+               uit->reverse_byte_order = lit->reverse_byte_order;
+               uit->base = lit->base;
+               if (serialize_string_encoding(&uit->encoding, lit->encoding))
+                       return -EINVAL;
+               uit->alignment = lit->alignment;
+               *uatype = ustctl_atype_integer;
+               break;
+       }
+       case atype_string:
+       {
+               if (serialize_string_encoding(&ubt->string.encoding,
+                               lbt->string.encoding))
+                       return -EINVAL;
+               *uatype = ustctl_atype_string;
+               break;
+       }
+       case atype_float:
+       {
+               struct ustctl_float_type *uft;
+               const struct lttng_float_type *lft;
+
+               uft = &ubt->_float;
+               lft = &lbt->_float;
+               uft->exp_dig = lft->exp_dig;
+               uft->mant_dig = lft->mant_dig;
+               uft->alignment = lft->alignment;
+               uft->reverse_byte_order = lft->reverse_byte_order;
+               *uatype = ustctl_atype_float;
+               break;
+       }
+       case atype_enum:
+       case atype_array:
+       case atype_sequence:
+       default:
+               return -EINVAL;
+       }
+       return 0;
+}
+
+static
+int serialize_one_type(struct ustctl_type *ut, const struct lttng_type *lt)
+{
+       int ret;
+
+       switch (lt->atype) {
+       case atype_integer:
+       case atype_float:
+       case atype_string:
+               ret = serialize_basic_type(&ut->atype, lt->atype,
+                       &ut->u.basic, &lt->u.basic);
+               if (ret)
+                       return ret;
+               break;
+       case atype_array:
+       {
+               struct ustctl_basic_type *ubt;
+               const struct lttng_basic_type *lbt;
+               int ret;
+
+               ubt = &ut->u.array.elem_type;
+               lbt = &lt->u.array.elem_type;
+               ut->u.array.length = lt->u.array.length;
+               ret = serialize_basic_type(&ubt->atype, lbt->atype,
+                       &ubt->u.basic, &lbt->u.basic);
+               if (ret)
+                       return -EINVAL;
+               ut->atype = ustctl_atype_array;
+               break;
+       }
+       case atype_sequence:
+       {
+               struct ustctl_basic_type *ubt;
+               const struct lttng_basic_type *lbt;
+               int ret;
+
+               ubt = &ut->u.sequence.length_type;
+               lbt = &lt->u.sequence.length_type;
+               ret = serialize_basic_type(&ubt->atype, lbt->atype,
+                       &ubt->u.basic, &lbt->u.basic);
+               if (ret)
+                       return -EINVAL;
+               ubt = &ut->u.sequence.elem_type;
+               lbt = &lt->u.sequence.elem_type;
+               ret = serialize_basic_type(&ubt->atype, lbt->atype,
+                       &ubt->u.basic, &lbt->u.basic);
+               if (ret)
+                       return -EINVAL;
+               ut->atype = ustctl_atype_sequence;
+               break;
+       }
+       case atype_enum:
+       default:
+               return -EINVAL;
+       }
+       return 0;
+}
+
+static
+int serialize_fields(size_t *_nr_write_fields,
+               struct ustctl_field **ustctl_fields,
+               size_t nr_fields,
+               const struct lttng_event_field *lttng_fields)
+{
+       struct ustctl_field *fields;
+       int i, ret;
+       size_t nr_write_fields = 0;
+
+       fields = zmalloc(nr_fields * sizeof(*fields));
+       if (!fields)
+               return -ENOMEM;
+
+       for (i = 0; i < nr_fields; i++) {
+               struct ustctl_field *f;
+               const struct lttng_event_field *lf;
+
+               f = &fields[nr_write_fields];
+               lf = &lttng_fields[i];
+
+               /* skip 'nowrite' fields */
+               if (lf->nowrite)
+                       continue;
+               strncpy(f->name, lf->name, LTTNG_UST_SYM_NAME_LEN);
+               f->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
+               ret = serialize_one_type(&f->type, &lf->type);
+               if (ret)
+                       goto error_type;
+               nr_write_fields++;
+       }
+
+       *_nr_write_fields = nr_write_fields;
+       *ustctl_fields = fields;
+       return 0;
+
+error_type:
+       free(fields);
+       return ret;
+}
+
+static
+int serialize_ctx_fields(size_t *_nr_write_fields,
+               struct ustctl_field **ustctl_fields,
+               size_t nr_fields,
+               const struct lttng_ctx_field *lttng_fields)
+{
+       struct ustctl_field *fields;
+       int i, ret;
+       size_t nr_write_fields = 0;
+
+       fields = zmalloc(nr_fields * sizeof(*fields));
+       if (!fields)
+               return -ENOMEM;
+
+       for (i = 0; i < nr_fields; i++) {
+               struct ustctl_field *f;
+               const struct lttng_event_field *lf;
+
+               f = &fields[nr_write_fields];
+               lf = &lttng_fields[i].event_field;
+
+               /* skip 'nowrite' fields */
+               if (lf->nowrite)
+                       continue;
+               strncpy(f->name, lf->name, LTTNG_UST_SYM_NAME_LEN);
+               f->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
+               ret = serialize_one_type(&f->type, &lf->type);
+               if (ret)
+                       goto error_type;
+               nr_write_fields++;
+       }
+
+       *_nr_write_fields = nr_write_fields;
+       *ustctl_fields = fields;
+       return 0;
+
+error_type:
+       free(fields);
+       return ret;
+}
+
+/*
+ * Returns 0 on success, negative error value on error.
+ */
+int ustcomm_register_event(int sock,
+       int session_objd,               /* session descriptor */
+       int channel_objd,               /* channel descriptor */
+       const char *event_name,         /* event name (input) */
+       int loglevel,
+       const char *signature,          /* event signature (input) */
+       size_t nr_fields,               /* fields */
+       const struct lttng_event_field *lttng_fields,
+       const char *model_emf_uri,
+       uint32_t *id)                   /* event id (output) */
+{
+       ssize_t len;
+       struct {
+               struct ustcomm_notify_hdr header;
+               struct ustcomm_notify_event_msg m;
+       } msg;
+       struct {
+               struct ustcomm_notify_hdr header;
+               struct ustcomm_notify_event_reply r;
+       } reply;
+       size_t signature_len, fields_len, model_emf_uri_len;
+       struct ustctl_field *fields = NULL;
+       size_t nr_write_fields = 0;
+       int ret;
+
+       memset(&msg, 0, sizeof(msg));
+       msg.header.notify_cmd = USTCTL_NOTIFY_CMD_EVENT;
+       msg.m.session_objd = session_objd;
+       msg.m.channel_objd = channel_objd;
+       strncpy(msg.m.event_name, event_name, LTTNG_UST_SYM_NAME_LEN);
+       msg.m.event_name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
+       msg.m.loglevel = loglevel;
+       signature_len = strlen(signature) + 1;
+       msg.m.signature_len = signature_len;
+
+       /* Calculate fields len, serialize fields. */
+       if (nr_fields > 0) {
+               ret = serialize_fields(&nr_write_fields, &fields,
+                               nr_fields, lttng_fields);
+               if (ret)
+                       return ret;
+       }
+
+       fields_len = sizeof(*fields) * nr_write_fields;
+       msg.m.fields_len = fields_len;
+       if (model_emf_uri) {
+               model_emf_uri_len = strlen(model_emf_uri) + 1;
+       } else {
+               model_emf_uri_len = 0;
+       }
+       msg.m.model_emf_uri_len = model_emf_uri_len;
+       len = ustcomm_send_unix_sock(sock, &msg, sizeof(msg));
+       if (len > 0 && len != sizeof(msg)) {
+               free(fields);
+               return -EIO;
+       }
+       if (len < 0) {
+               free(fields);
+               return len;
+       }
+
+       /* send signature */
+       len = ustcomm_send_unix_sock(sock, signature, signature_len);
+       if (len > 0 && len != signature_len) {
+               free(fields);
+               return -EIO;
+       }
+       if (len < 0) {
+               free(fields);
+               return len;
+       }
+
+       /* send fields */
+       if (fields_len > 0) {
+               len = ustcomm_send_unix_sock(sock, fields, fields_len);
+               free(fields);
+               if (len > 0 && len != fields_len) {
+                       return -EIO;
+               }
+               if (len < 0) {
+                       return len;
+               }
+       } else {
+               free(fields);
+       }
+
+       if (model_emf_uri_len) {
+               /* send model_emf_uri */
+               len = ustcomm_send_unix_sock(sock, model_emf_uri,
+                               model_emf_uri_len);
+               if (len > 0 && len != model_emf_uri_len)
+                       return -EIO;
+               if (len < 0)
+                       return len;
+       }
+
+       /* receive reply */
+       len = ustcomm_recv_unix_sock(sock, &reply, sizeof(reply));
+       switch (len) {
+       case 0: /* orderly shutdown */
+               return -EPIPE;
+       case sizeof(reply):
+               if (reply.header.notify_cmd != msg.header.notify_cmd) {
+                       ERR("Unexpected result message command "
+                               "expected: %u vs received: %u\n",
+                               msg.header.notify_cmd, reply.header.notify_cmd);
+                       return -EINVAL;
+               }
+               if (reply.r.ret_code > 0)
+                       return -EINVAL;
+               if (reply.r.ret_code < 0)
+                       return reply.r.ret_code;
+               *id = reply.r.event_id;
+               DBG("Sent register event notification for name \"%s\": ret_code %d, event_id %u\n",
+                       event_name, reply.r.ret_code, reply.r.event_id);
+               return 0;
+       default:
+               if (len < 0) {
+                       /* Transport level error */
+                       if (errno == EPIPE || errno == ECONNRESET)
+                               len = -errno;
+                       return len;
+               } else {
+                       ERR("incorrect message size: %zd\n", len);
+                       return len;
+               }
+       }
+}
+
+/*
+ * Returns 0 on success, negative error value on error.
+ * Returns -EPIPE or -ECONNRESET if other end has hung up.
+ */
+int ustcomm_register_channel(int sock,
+       int session_objd,               /* session descriptor */
+       int channel_objd,               /* channel descriptor */
+       size_t nr_ctx_fields,
+       const struct lttng_ctx_field *ctx_fields,
+       uint32_t *chan_id,              /* channel id (output) */
+       int *header_type)               /* header type (output) */
+{
+       ssize_t len;
+       struct {
+               struct ustcomm_notify_hdr header;
+               struct ustcomm_notify_channel_msg m;
+       } msg;
+       struct {
+               struct ustcomm_notify_hdr header;
+               struct ustcomm_notify_channel_reply r;
+       } reply;
+       size_t fields_len;
+       struct ustctl_field *fields = NULL;
+       int ret;
+       size_t nr_write_fields = 0;
+
+       memset(&msg, 0, sizeof(msg));
+       msg.header.notify_cmd = USTCTL_NOTIFY_CMD_CHANNEL;
+       msg.m.session_objd = session_objd;
+       msg.m.channel_objd = channel_objd;
+
+       /* Calculate fields len, serialize fields. */
+       if (nr_ctx_fields > 0) {
+               ret = serialize_ctx_fields(&nr_write_fields, &fields,
+                               nr_ctx_fields, ctx_fields);
+               if (ret)
+                       return ret;
+       }
+
+       fields_len = sizeof(*fields) * nr_write_fields;
+       msg.m.ctx_fields_len = fields_len;
+       len = ustcomm_send_unix_sock(sock, &msg, sizeof(msg));
+       if (len > 0 && len != sizeof(msg)) {
+               free(fields);
+               return -EIO;
+       }
+       if (len < 0) {
+               free(fields);
+               return len;
+       }
+
+       /* send fields */
+       if (fields_len > 0) {
+               len = ustcomm_send_unix_sock(sock, fields, fields_len);
+               free(fields);
+               if (len > 0 && len != fields_len) {
+                       return -EIO;
+               }
+               if (len < 0) {
+                       return len;
+               }
+       } else {
+               free(fields);
+       }
+
+       len = ustcomm_recv_unix_sock(sock, &reply, sizeof(reply));
+       switch (len) {
+       case 0: /* orderly shutdown */
+               return -EPIPE;
+       case sizeof(reply):
+               if (reply.header.notify_cmd != msg.header.notify_cmd) {
+                       ERR("Unexpected result message command "
+                               "expected: %u vs received: %u\n",
+                               msg.header.notify_cmd, reply.header.notify_cmd);
+                       return -EINVAL;
+               }
+               if (reply.r.ret_code > 0)
+                       return -EINVAL;
+               if (reply.r.ret_code < 0)
+                       return reply.r.ret_code;
+               *chan_id = reply.r.chan_id;
+               switch (reply.r.header_type) {
+               case 1:
+               case 2:
+                       *header_type = reply.r.header_type;
+                       break;
+               default:
+                       ERR("Unexpected channel header type %u\n",
+                               reply.r.header_type);
+                       return -EINVAL;
+               }
+               DBG("Sent register channel notification: chan_id %d, header_type %d\n",
+                       reply.r.chan_id, reply.r.header_type);
+               return 0;
+       default:
+               if (len < 0) {
+                       /* Transport level error */
+                       if (errno == EPIPE || errno == ECONNRESET)
+                               len = -errno;
+                       return len;
+               } else {
+                       ERR("incorrect message size: %zd\n", len);
+                       return len;
+               }
+       }
+}
+
+/*
+ * Set socket reciving timeout.
+ */
+int ustcomm_setsockopt_rcv_timeout(int sock, unsigned int msec)
+{
+       int ret;
+       struct timeval tv;
+
+       tv.tv_sec = msec / 1000;
+       tv.tv_usec = (msec * 1000 % 1000000);
+
+       ret = setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
+       if (ret < 0) {
+               PERROR("setsockopt SO_RCVTIMEO");
+               ret = -errno;
+       }
+
+       return ret;
+}
+
+/*
+ * Set socket sending timeout.
+ */
+int ustcomm_setsockopt_snd_timeout(int sock, unsigned int msec)
+{
+       int ret;
+       struct timeval tv;
+
+       tv.tv_sec = msec / 1000;
+       tv.tv_usec = (msec * 1000) % 1000000;
+
+       ret = setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv));
+       if (ret < 0) {
+               PERROR("setsockopt SO_SNDTIMEO");
+               ret = -errno;
+       }
+
+       return ret;
+}
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