Exosip源码学习

随手记录一下exosip的学习过程：

1. nist 非invite事件服务端处理，nict 非invite事件客户端处理，ist invite服务器处理，ict invite客户端处理。

2. 状态机处理链表，每种状态对应一个处理方式，当事务处于trying状态时，根据超时类型处理，这种链表结构实属优秀了。。

typedef struct _transition_t transition_t;

struct _transition_t {
state_t state;
type_t type;
void (*method) (void *, void *);
struct _transition_t *next;
struct _transition_t *parent;
};

transition_t nict_transition[12] = {
{
NICT_PRE_TRYING,
SND_REQUEST,
(void (*)(void *, void *)) &nict_snd_request,
&nict_transition[1], NULL}
,
{
NICT_TRYING,
TIMEOUT_F,
(void (*)(void *, void *)) &osip_nict_timeout_f_event,
&nict_transition[2], NULL}
,
{
NICT_TRYING,
TIMEOUT_E,
(void (*)(void *, void *)) &osip_nict_timeout_e_event,
&nict_transition[3], NULL}
,
{
NICT_TRYING,
RCV_STATUS_1XX,
(void (*)(void *, void *)) &nict_rcv_1xx,
&nict_transition[4], NULL}
,
{
NICT_TRYING,
RCV_STATUS_2XX,
(void (*)(void *, void *)) &nict_rcv_23456xx,
&nict_transition[5], NULL}
,
{
NICT_TRYING,
RCV_STATUS_3456XX,
(void (*)(void *, void *)) &nict_rcv_23456xx,
&nict_transition[6], NULL}
,
{
NICT_PROCEEDING,
TIMEOUT_F,
(void (*)(void *, void *)) &osip_nict_timeout_f_event,
&nict_transition[7], NULL}
,
{
NICT_PROCEEDING,
TIMEOUT_E,
(void (*)(void *, void *)) &osip_nict_timeout_e_event,
&nict_transition[8], NULL}
,
{
NICT_PROCEEDING,
RCV_STATUS_1XX,
(void (*)(void *, void *)) &nict_rcv_1xx,
&nict_transition[9], NULL}
,
{
NICT_PROCEEDING,
RCV_STATUS_2XX,
(void (*)(void *, void *)) &nict_rcv_23456xx,
&nict_transition[10], NULL}
,
{
NICT_PROCEEDING,
RCV_STATUS_3456XX,
(void (*)(void *, void *)) &nict_rcv_23456xx,
&nict_transition[11], NULL}
,
{
NICT_COMPLETED,
TIMEOUT_K,
(void (*)(void *, void *)) &osip_nict_timeout_k_event,
NULL, NULL}
};

exosip线程执行事件

eXosip_execute (struct eXosip_t *excontext)
{
       ...
       osip_nist_execute (excontext->j_osip);
       osip_nict_execute (excontext->j_osip);
       osip_ist_execute (excontext->j_osip);
       osip_ict_execute (excontext->j_osip);
       ...
}

int osip_nict_execute (osip_t * osip)
{
for (index = 0; index < len; ++index) {
transaction = (osip_transaction_t *) array[index];
more_event = 1;
do {
se = (osip_event_t *) osip_fifo_tryget (transaction->transactionff);
if (se == NULL) /* no more event for this transaction */
more_event = 0;
else
osip_transaction_execute (transaction, se);
}
while (more_event == 1);
}
}

NICT_PRE_TRYING状态调用nict_snd_request 直接发送并更新状态NICT_TRYING，并设置启动的定时器timer_e_start和timer_e_length，由于没有使用tcp等可靠协议，所以timer_e_start没有修改，使用的默认值 500ms；

int
__osip_nict_init (osip_nict_t ** nict, osip_t * osip, osip_message_t * request)
{
//if (osip_strcasecmp (proto, "TCP") != 0 && osip_strcasecmp (proto, "TLS") != 0 && osip_strcasecmp (proto, "SCTP") != 0) {(*nict)->timer_e_length = DEFAULT_T1;(*nict)->timer_k_length = DEFAULT_T4;(*nict)->timer_e_start.tv_sec = -1;(*nict)->timer_k_start.tv_sec = -1;       /* not started */}else {                      /* reliable protocol is used: */(*nict)->timer_e_length = DEFAULT_T1;(*nict)->timer_k_length = 0;      /* MUST do the transition immediatly */(*nict)->timer_e_start.tv_sec = -1;(*nict)->timer_k_start.tv_sec = -1;       /* not started */}}
}void
nict_snd_request (osip_transaction_t * nict, osip_event_t * evt)
{int i;osip_t *osip = (osip_t *) nict->config;/* Here we have ict->orig_request == NULL */nict->orig_request = evt->sip;i = osip->cb_send_message (nict, evt->sip, nict->nict_context->destination, nict->nict_context->port, nict->out_socket);#ifndef USE_BLOCKINGSOCKET/*stop timer E in reliable transport - non blocking socket: the message was just sent*/{osip_via_t *via;char *proto;int k;k = osip_message_get_via (nict->orig_request, 0, &via);   /* get top via */if (k < 0) {nict_handle_transport_error (nict, -1);return;}proto = via_get_protocol (via);if (proto == NULL) {nict_handle_transport_error (nict, -1);return;}if (i == 0) {               /* but message was really sent */if (osip_strcasecmp (proto, "TCP") != 0 && osip_strcasecmp (proto, "TLS") != 0 && osip_strcasecmp (proto, "SCTP") != 0) {}else {                    /* reliable protocol is used: */nict->nict_context->timer_e_length = -1;        /* E is not ACTIVE */nict->nict_context->timer_e_start.tv_sec = -1;}} else {if (osip_strcasecmp (proto, "TCP") != 0 && osip_strcasecmp (proto, "TLS") != 0 && osip_strcasecmp (proto, "SCTP") != 0) {}else {                    /* reliable protocol is used: */nict->nict_context->timer_e_length = DEFAULT_T1_TCP_PROGRESS;}}}
#endifif (nict->nict_context->timer_e_length > 0) {osip_gettimeofday (&nict->nict_context->timer_e_start, NULL);add_gettimeofday (&nict->nict_context->timer_e_start, nict->nict_context->timer_e_length);}__osip_transaction_set_state (nict, NICT_TRYING);}else {nict_handle_transport_error (nict, i);}
}

下一次循环处理，会先调用osip_timers_nict_execute判断，如果符合状态并且超时，则会添加处理任务到transactionff队列中等待处理，


void
osip_timers_nict_execute (osip_t * osip)
{osip_transaction_t *tr;osip_list_iterator_t iterator;/* handle nict timers */tr = (osip_transaction_t *) osip_list_get_first (&osip->osip_nict_transactions, &iterator);while (osip_list_iterator_has_elem (iterator)) {osip_event_t *evt;evt = __osip_nict_need_timer_k_event (tr->nict_context, tr->state, tr->transactionid);if (evt != NULL)osip_fifo_add (tr->transactionff, evt);else {evt = __osip_nict_need_timer_f_event (tr->nict_context, tr->state, tr->transactionid);if (evt != NULL)osip_fifo_add (tr->transactionff, evt);else {evt = __osip_nict_need_timer_e_event (tr->nict_context, tr->state, tr->transactionid);if (evt != NULL)osip_fifo_add (tr->transactionff, evt);}}tr = (osip_transaction_t *) osip_list_get_next (&iterator);}
}

NICT_TRYING有多种定时器，会根据超时类型做不同处理，TIMEOUT_E 每隔两倍时间发一次，TIMEOUT_F直接terminate。

void
osip_nict_timeout_e_event (osip_transaction_t * nict, osip_event_t * evt)
{osip_t *osip = (osip_t *) nict->config;int i;/* reset timer */if (nict->state == NICT_TRYING) {if (nict->nict_context->timer_e_length < DEFAULT_T1)nict->nict_context->timer_e_length = nict->nict_context->timer_e_length + DEFAULT_T1_TCP_PROGRESS;elsenict->nict_context->timer_e_length = nict->nict_context->timer_e_length * 2;if (nict->nict_context->timer_e_length > DEFAULT_T2)nict->nict_context->timer_e_length = DEFAULT_T2;}else                          /* in PROCEEDING STATE, TIMER is always DEFAULT_T2 */nict->nict_context->timer_e_length = DEFAULT_T2;osip_gettimeofday (&nict->nict_context->timer_e_start, NULL);add_gettimeofday (&nict->nict_context->timer_e_start, nict->nict_context->timer_e_length);/* retransmit REQUEST */i = osip->cb_send_message (nict, nict->orig_request, nict->nict_context->destination, nict->nict_context->port, nict->out_socket);if (i < 0) {nict_handle_transport_error (nict, i);return;}if (i == 0)                   /* but message was really sent */__osip_message_callback (OSIP_NICT_REQUEST_SENT_AGAIN, nict, nict->orig_request);
}

struct osip_nict {
int timer_e_length; /**< Timer E A=T1, A=2xT1... (unreliable only) */
struct timeval timer_e_start; /**< Timer E (retransmission) */
int timer_f_length; /**< Timer F B = 64* T1 */
struct timeval timer_f_start; /**< Timer F (fire when transaction timeout) */
int timer_k_length; /**< Timer K K = T4 (else = 0) */
struct timeval timer_k_start; /**< Timer K */
char *destination; /**< IP used to send requests */
int port; /**< port of next hop */

};

发送request请求的时候，会把transaction添加到NICT对应的处理队列，并返回TID事务ID。

int eXosip_message_send_request (struct eXosip_t *excontext, osip_message_t * message)
{
osip_transaction_t *transaction;
osip_event_t *sipevent;
int i;

i = _eXosip_transaction_init (excontext, &transaction, NICT, excontext->j_osip, message);
saction_add_event (transaction, sipevent);

_eXosip_wakeup (excontext);
return transaction->transactionid; /* return TID (>0) instead of OSIP_SUCCESS; */
}

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