PJSIP学习笔记——PJSUA层发起呼叫的主要流程
在上一篇学习笔记 从simple_pjsua.c示例程序了解PJSUA-LIB的基本使用流程中,使用了PJSUA层的
pjsua_call_make_call来发起一个呼叫,那么这个发起呼叫的流程是怎样的呢?先来看看这个函数:
- /*
- * Make outgoing call to the specified URI using the specified account.
- */
- PJ_DEF(pj_status_t) pjsua_call_make_call(pjsua_acc_id acc_id,
- const pj_str_t *dest_uri,
- const pjsua_call_setting *opt,
- void *user_data,
- const pjsua_msg_data *msg_data,
- pjsua_call_id *p_call_id)
- {
- pj_pool_t *tmp_pool = NULL;
- pjsip_dialog *dlg = NULL;
- pjsua_acc *acc;
- pjsua_call *call;
- int call_id = -1;
- pj_str_t contact;
- pj_status_t status;
- /* Check that account is valid */
- PJ_ASSERT_RETURN(acc_id>=0 || acc_id<(int)PJ_ARRAY_SIZE(pjsua_var.acc),
- PJ_EINVAL);
- /* Check arguments */
- PJ_ASSERT_RETURN(dest_uri, PJ_EINVAL);
- PJ_LOG(4,(THIS_FILE, "Making call with acc #%d to %.*s", acc_id,
- (int)dest_uri->slen, dest_uri->ptr));
- pj_log_push_indent();
- PJSUA_LOCK();
- // 创建声音设备
- /* Create sound port if none is instantiated, to check if sound device
- * can be used. But only do this with the conference bridge, as with
- * audio switchboard (i.e. APS-Direct), we can only open the sound
- * device once the correct format has been known
- */
- if (!pjsua_var.is_mswitch && pjsua_var.snd_port==NULL &&
- pjsua_var.null_snd==NULL && !pjsua_var.no_snd)
- {
- status = pjsua_set_snd_dev(pjsua_var.cap_dev, pjsua_var.play_dev);
- if (status != PJ_SUCCESS)
- goto on_error;
- }
- // 检查SIP帐号
- acc = &pjsua_var.acc[acc_id];
- if (!acc->valid) {
- pjsua_perror(THIS_FILE, "Unable to make call because account "
- "is not valid", PJ_EINVALIDOP);
- status = PJ_EINVALIDOP;
- goto on_error;
- }
- // 创建呼叫标识
- /* Find free call slot. */
- call_id = alloc_call_id();
- if (call_id == PJSUA_INVALID_ID) {
- pjsua_perror(THIS_FILE, "Error making call", PJ_ETOOMANY);
- status = PJ_ETOOMANY;
- goto on_error;
- }
- // 复位呼叫参数
- /* Clear call descriptor */
- reset_call(call_id);
- call = &pjsua_var.calls[call_id];
- /* Associate session with account */
- call->acc_id = acc_id;
- call->call_hold_type = acc->cfg.call_hold_type;
- // 设置呼叫参数
- /* Apply call setting */
- status = apply_call_setting(call, opt, NULL);
- if (status != PJ_SUCCESS) {
- pjsua_perror(THIS_FILE, "Failed to apply call setting", status);
- goto on_error;
- }
- /* Create temporary pool */
- tmp_pool = pjsua_pool_create("tmpcall10", 512, 256);
- /* Verify that destination URI is valid before calling
- * pjsua_acc_create_uac_contact, or otherwise there
- * a misleading "Invalid Contact URI" error will be printed
- * when pjsua_acc_create_uac_contact() fails.
- */
- if (1) {
- pjsip_uri *uri;
- pj_str_t dup;
- // 分析被叫SIP号码
- pj_strdup_with_null(tmp_pool, &dup, dest_uri);
- uri = pjsip_parse_uri(tmp_pool, dup.ptr, dup.slen, 0);
- if (uri == NULL) {
- pjsua_perror(THIS_FILE, "Unable to make call",
- PJSIP_EINVALIDREQURI);
- status = PJSIP_EINVALIDREQURI;
- goto on_error;
- }
- }
- /* Mark call start time. */
- pj_gettimeofday(&call->start_time);
- /* Reset first response time */
- call->res_time.sec = 0;
- // 创建Contact头域
- /* Create suitable Contact header unless a Contact header has been
- * set in the account.
- */
- if (acc->contact.slen) {
- contact = acc->contact;
- } else {
- status = pjsua_acc_create_uac_contact(tmp_pool, &contact,
- acc_id, dest_uri);
- if (status != PJ_SUCCESS) {
- pjsua_perror(THIS_FILE, "Unable to generate Contact header",
- status);
- goto on_error;
- }
- }
- // 创建SIP对话(Dialog)
- /* Create outgoing dialog: */
- status = pjsip_dlg_create_uac( pjsip_ua_instance(),
- &acc->cfg.id, &contact,
- dest_uri, dest_uri, &dlg);
- if (status != PJ_SUCCESS) {
- pjsua_perror(THIS_FILE, "Dialog creation failed", status);
- goto on_error;
- }
- /* Increment the dialog's lock otherwise when invite session creation
- * fails the dialog will be destroyed prematurely.
- */
- pjsip_dlg_inc_lock(dlg);
- // 设置Via头域
- if (acc->cfg.allow_via_rewrite && acc->via_addr.host.slen > 0)
- pjsip_dlg_set_via_sent_by(dlg, &acc->via_addr, acc->via_tp);
- // 设置安全级别,安全级别有何作用?
- /* Calculate call's secure level */
- call->secure_level = get_secure_level(acc_id, dest_uri);
- // 设置用户数据,用户数据是什么?
- /* Attach user data */
- call->user_data = user_data;
- // 复制消息数据,消息数据有何作用?
- /* Store variables required for the callback after the async
- * media transport creation is completed.
- */
- if (msg_data) {
- call->async_call.call_var.out_call.msg_data = pjsua_msg_data_clone(
- dlg->pool, msg_data);
- }
- // 保存对话信息
- call->async_call.dlg = dlg;
- /* Temporarily increment dialog session. Without this, dialog will be
- * prematurely destroyed if dec_lock() is called on the dialog before
- * the invite session is created.
- */
- pjsip_dlg_inc_session(dlg, &pjsua_var.mod);
- // 初始化媒体通道
- /* Init media channel */
- status = pjsua_media_channel_init(call->index, PJSIP_ROLE_UAC,
- call->secure_level, dlg->pool,
- NULL, NULL, PJ_TRUE,
- &on_make_call_med_tp_complete);
- // 调用媒体传输回调函数
- if (status == PJ_SUCCESS) {
- status = on_make_call_med_tp_complete(call->index, NULL);
- if (status != PJ_SUCCESS)
- goto on_error;
- } else if (status != PJ_EPENDING) {
- pjsua_perror(THIS_FILE, "Error initializing media channel", status);
- pjsip_dlg_dec_session(dlg, &pjsua_var.mod);
- goto on_error;
- }
- /* Done. */
- if (p_call_id)
- *p_call_id = call_id;
- pjsip_dlg_dec_lock(dlg);
- pj_pool_release(tmp_pool);
- PJSUA_UNLOCK();
- pj_log_pop_indent();
- return PJ_SUCCESS;
- on_error:
- if (dlg) {
- /* This may destroy the dialog */
- pjsip_dlg_dec_lock(dlg);
- }
- if (call_id != -1) {
- pjsua_media_channel_deinit(call_id);
- reset_call(call_id);
- }
- pjsua_check_snd_dev_idle();
- if (tmp_pool)
- pj_pool_release(tmp_pool);
- PJSUA_UNLOCK();
- pj_log_pop_indent();
- return status;
- }
我们先来看看如何分配一个呼叫标识:
- /* Allocate one call id */
- static pjsua_call_id alloc_call_id(void)
- {
- pjsua_call_id cid;
- #if 1
- /* New algorithm: round-robin */
- if (pjsua_var.next_call_id >= (int)pjsua_var.ua_cfg.max_calls ||
- pjsua_var.next_call_id < 0)
- {
- pjsua_var.next_call_id = 0;
- }
- // 从next_call_id到max_calls之间找一个空闲的calls数组元素
- for (cid=pjsua_var.next_call_id;
- cid<(int)pjsua_var.ua_cfg.max_calls;
- ++cid)
- {
- if (pjsua_var.calls[cid].inv == NULL &&
- pjsua_var.calls[cid].async_call.dlg == NULL)
- {
- ++pjsua_var.next_call_id;
- return cid;
- }
- }
- // 从0到next_call_id之间找一个空闲的calls数组元素
- for (cid=0; cid < pjsua_var.next_call_id; ++cid) {
- if (pjsua_var.calls[cid].inv == NULL &&
- pjsua_var.calls[cid].async_call.dlg == NULL)
- {
- ++pjsua_var.next_call_id;
- return cid;
- }
- }
- #else
- /* Old algorithm */
- for (cid=0; cid<(int)pjsua_var.ua_cfg.max_calls; ++cid) {
- if (pjsua_var.calls[cid].inv == NULL)
- return cid;
- }
- #endif
- return PJSUA_INVALID_ID;
- }
从上面的函数来看,这里的分配呼叫标识只是在calls数据中寻找一个空闲的单元(用于存放呼叫数据),这个呼叫标识并不是SIP协议里面的CALL ID的概念。
reset_call函数就是将呼叫参数设置为0值:
- *
- * Reset call descriptor.
- */
- static void reset_call(pjsua_call_id id)
- {
- pjsua_call *call = &pjsua_var.calls[id];
- unsigned i;
- pj_bzero(call, sizeof(*call));
- call->index = id;
- call->last_text.ptr = call->last_text_buf_;
- for (i=0; i<PJ_ARRAY_SIZE(call->media); ++i) {
- pjsua_call_media *call_med = &call->media[i];
- call_med->ssrc = pj_rand();
- call_med->strm.a.conf_slot = PJSUA_INVALID_ID;
- call_med->strm.v.cap_win_id = PJSUA_INVALID_ID;
- call_med->strm.v.rdr_win_id = PJSUA_INVALID_ID;
- call_med->call = call;
- call_med->idx = i;
- call_med->tp_auto_del = PJ_TRUE;
- }
- pjsua_call_setting_default(&call->opt);
- pj_timer_entry_init(&call->reinv_timer, PJ_FALSE,
- (void*)(pj_size_t)id, &reinv_timer_cb);
- }
设置呼叫参数:
- static pj_status_t apply_call_setting(pjsua_call *call,
- const pjsua_call_setting *opt,
- const pjmedia_sdp_session *rem_sdp)
- {
- pj_assert(call);
- if (!opt)
- return PJ_SUCCESS;
- #if !PJMEDIA_HAS_VIDEO
- pj_assert(opt->vid_cnt == 0);
- #endif
- call->opt = *opt;
- // 如果呼叫已建立,则设置本端的对话角色
- // 如果有远端SDP,则本端为UAS(User Agent Server),否则为UAC
- /* If call is established, reinit media channel */
- if (call->inv && call->inv->state == PJSIP_INV_STATE_CONFIRMED) {
- pjsip_role_e role = rem_sdp? PJSIP_ROLE_UAS : PJSIP_ROLE_UAC;
- pj_status_t status;
- // 初始化媒体通道
- status = pjsua_media_channel_init(call->index, role,
- call->secure_level,
- call->inv->pool_prov,
- rem_sdp, NULL,
- PJ_FALSE, NULL);
- if (status != PJ_SUCCESS) {
- pjsua_perror(THIS_FILE, "Error re-initializing media channel",
- status);
- return status;
- }
- }
- return PJ_SUCCESS;
- }
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