webrtc入门：8.coturn流程

大家好，我是讯享网，很高兴认识大家。

对于局域网中的webrtc是不需要coturn，因为他们自己进行视频流的传输，但通常的应用场景，在同一个局域网下概率是比较低的，因此我们需要把流推到服务器上，另外一端在从服务器把流拉下来。coturn做为turnserver做的是这一部分的工作。当然coturn也可以作为 stun服务器，这篇文章先不讲，只讲turnserver这部分的内容。

turnserver的原理是根据webrtc的协议而定的，最主要的功能就是转发webrtc上的数据流，在转发数据流中，最关键的是两样，一个是创建流端口连接，一个是匹配端口。

当webrtc的客户端配置上了ICE_SERVER 以后，客户端会去ICE_SERVER 请求一个端口用来传递数据流，这就是所谓的ice，在互换了ice以后，会选出一个通路来匹配到另一端的通路，数据在服务端中进行转发传递。

这也就是最重要的两个环节，创建流通路和匹配通道。

1.创建流通路

webrtc的客户端向服务器发起连接，通过命令告诉服务器他需要的东西。

static int handle_turn_command(turn_turnserver *server, ts_ur_super_session *ss, ioa_net_data *in_buffer, ioa_network_buffer_handle nbh, int *resp_constructed, int can_resume) { ... if (!err_code && !(*resp_constructed) && !no_response) { switch (method){ case STUN_METHOD_ALLOCATE: { handle_turn_allocate(server, ss, &tid, resp_constructed, &err_code, &reason, unknown_attrs, &ua_num, in_buffer, nbh); if(server->verbose) { log_method(ss, "ALLOCATE", err_code, reason); } break; } ... return 0; }

讯享网

在对 turn 的命令进行处理时，STUN_METHOD_ALLOCATE告诉服务器，需要分配一个新的通道。

讯享网static int handle_turn_allocate(turn_turnserver *server, ts_ur_super_session *ss, stun_tid *tid, int *resp_constructed, int *err_code, const u08bits reason, u16bits *unknown_attrs, u16bits *ua_num, ioa_net_data *in_buffer, ioa_network_buffer_handle nbh) { ... if(!(*err_code)) { if(!af4 && !af6) { int af4res = create_relay_connection(server, ss, lifetime, STUN_ATTRIBUTE_REQUESTED_ADDRESS_FAMILY_VALUE_DEFAULT, transport, even_port, in_reservation_token, &out_reservation_token, err_code, reason, tcp_peer_accept_connection); if(af4res<0) { set_relay_session_failure(alloc,AF_INET); if(!(*err_code)) { *err_code = 437; } } } else if(!af4 && af6) { int af6res = create_relay_connection(server, ss, lifetime, af6, transport, even_port, in_reservation_token, &out_reservation_token, err_code, reason, tcp_peer_accept_connection); if(af6res<0) { set_relay_session_failure(alloc,AF_INET6); if(!(*err_code)) { *err_code = 437; } } } else if(af4 && !af6) { int af4res = create_relay_connection(server, ss, lifetime, af4, transport, even_port, in_reservation_token, &out_reservation_token, err_code, reason, tcp_peer_accept_connection); if(af4res<0) { set_relay_session_failure(alloc,AF_INET); if(!(*err_code)) { *err_code = 437; } } } else { const u08bits *reason4 = NULL; const u08bits *reason6 = NULL; { int af4res = create_relay_connection(server, ss, lifetime, af4, transport, even_port, in_reservation_token, &out_reservation_token, &err_code4, &reason4, tcp_peer_accept_connection); if(af4res<0) { set_relay_session_failure(alloc,AF_INET); if(!err_code4) { err_code4 = 440; } } } { int af6res = create_relay_connection(server, ss, lifetime, af6, transport, even_port, in_reservation_token, &out_reservation_token, &err_code6, &reason6, tcp_peer_accept_connection); if(af6res<0) { set_relay_session_failure(alloc,AF_INET6); if(!err_code6) { err_code6 = 440; } } } if(err_code4 && err_code6) { if(reason4) { *err_code = err_code4; *reason = reason4; } else if(reason6) { *err_code = err_code6; *reason = reason6; } else { *err_code = err_code4; } } } } ... return 0; }

create_relay_connection 用来创建 relay的连接，具体在看看create_relay_connection 的内容。

static int create_relay_connection(turn_turnserver* server, ts_ur_super_session *ss, u32bits lifetime, int address_family, u08bits transport, int even_port, u64bits in_reservation_token, u64bits *out_reservation_token, int *err_code, const u08bits reason, accept_cb acb) { ... else { newelem = get_relay_session_ss(ss,get_family(address_family)); IOA_CLOSE_SOCKET(newelem->s); ns_bzero(newelem, sizeof(relay_endpoint_session)); newelem->s = NULL; int res = create_relay_ioa_sockets(server->e, ss->client_socket, address_family, transport, even_port, &(newelem->s), &rtcp_s, out_reservation_token, err_code, reason, acb, ss); if (res < 0) { if(!(*err_code)) *err_code = 508; if(!(*reason)) *reason = (const u08bits *)"Cannot create socket"; IOA_CLOSE_SOCKET(newelem->s); IOA_CLOSE_SOCKET(rtcp_s); return -1; } } ... /* RFC6156: do not use DF when IPv6 is involved: */ if((get_ioa_socket_address_family(newelem->s) == AF_INET6) || (get_ioa_socket_address_family(ss->client_socket) == AF_INET6)) set_do_not_use_df(newelem->s); if(get_ioa_socket_type(newelem->s) != TCP_SOCKET) { if(register_callback_on_ioa_socket(server->e, newelem->s, IOA_EV_READ,peer_input_handler, ss, 0)<0) { return -1; } } return 0; }

关键的代码在 create_relay_ioa_sockets 下，现在sockerts的字眼已经出现了，建立完成以后，设置了peer_input_handler的匹配回调接口。

讯享网int create_relay_ioa_sockets(ioa_engine_handle e, ioa_socket_handle client_s, int address_family, u08bits transport, int even_port, ioa_socket_handle *rtp_s, ioa_socket_handle *rtcp_s, uint64_t *out_reservation_token, int *err_code, const u08bits reason, accept_cb acb, void *acbarg) { ... for (iip = 0; iip < e->relays_number; ++iip) { ... addr_cpy(&rtcp_local_addr, &relay_addr); int i = 0; int port = 0; ioa_addr local_addr; addr_cpy(&local_addr, &relay_addr); for (i = 0; i < 0xFFFF; i++) { port = 0; rtcp_port = -1; if (even_port < 0) { port = turnipports_allocate(tp, transport, &relay_addr); } else { port = turnipports_allocate_even(tp, &relay_addr, even_port, out_reservation_token); if (port >= 0 && even_port > 0) { IOA_CLOSE_SOCKET(*rtcp_s); *rtcp_s = create_unbound_relay_ioa_socket(e, relay_addr.ss.sa_family, UDP_SOCKET, RELAY_RTCP_SOCKET); if (*rtcp_s == NULL) { perror("socket"); IOA_CLOSE_SOCKET(*rtp_s); addr_set_port(&local_addr, port); turnipports_release(tp, transport, &local_addr); rtcp_port = port + 1; addr_set_port(&rtcp_local_addr, rtcp_port); turnipports_release(tp, transport, &rtcp_local_addr); return -1; } sock_bind_to_device((*rtcp_s)->fd, (unsigned char*)e->relay_ifname); rtcp_port = port + 1; addr_set_port(&rtcp_local_addr, rtcp_port); if (bind_ioa_socket(*rtcp_s, &rtcp_local_addr, (transport == STUN_ATTRIBUTE_TRANSPORT_TCP_VALUE)) < 0) { addr_set_port(&local_addr, port); turnipports_release(tp, transport, &local_addr); turnipports_release(tp, transport, &rtcp_local_addr); rtcp_port = -1; IOA_CLOSE_SOCKET(*rtcp_s); continue; } } } if (port < 0) { IOA_CLOSE_SOCKET(*rtp_s); if (rtcp_s) IOA_CLOSE_SOCKET(*rtcp_s); rtcp_port = -1; break; } else { IOA_CLOSE_SOCKET(*rtp_s); *rtp_s = create_unbound_relay_ioa_socket(e, relay_addr.ss.sa_family, (transport == STUN_ATTRIBUTE_TRANSPORT_TCP_VALUE) ? TCP_SOCKET : UDP_SOCKET, RELAY_SOCKET); if (*rtp_s == NULL) { int rtcp_bound = 0; if (rtcp_s && *rtcp_s) { rtcp_bound = (*rtcp_s)->bound; IOA_CLOSE_SOCKET(*rtcp_s); } addr_set_port(&local_addr, port); turnipports_release(tp, transport, &local_addr); if (rtcp_port >= 0 && !rtcp_bound) { addr_set_port(&rtcp_local_addr, rtcp_port); turnipports_release(tp, transport, &rtcp_local_addr); } perror("socket"); return -1; } sock_bind_to_device((*rtp_s)->fd, (unsigned char*)e->relay_ifname); addr_set_port(&local_addr, port); if (bind_ioa_socket(*rtp_s, &local_addr, (transport == STUN_ATTRIBUTE_TRANSPORT_TCP_VALUE)) >= 0) { break; } else { IOA_CLOSE_SOCKET(*rtp_s); int rtcp_bound = 0; if (rtcp_s && *rtcp_s) { rtcp_bound = (*rtcp_s)->bound; IOA_CLOSE_SOCKET(*rtcp_s); } addr_set_port(&local_addr, port); turnipports_release(tp, transport, &local_addr); if (rtcp_port >= 0 && !rtcp_bound) { addr_set_port(&rtcp_local_addr, rtcp_port); turnipports_release(tp, transport, &rtcp_local_addr); } rtcp_port = -1; } } } } if (!(*rtp_s)) { TURN_LOG_FUNC(TURN_LOG_LEVEL_INFO, "%s: no available ports 3\n", __FUNCTION__); IOA_CLOSE_SOCKET(*rtp_s); if (rtcp_s) IOA_CLOSE_SOCKET(*rtcp_s); return -1; } set_accept_cb(*rtp_s, acb, acbarg); if (rtcp_s && *rtcp_s && out_reservation_token && *out_reservation_token) { if (rtcp_map_put(e->map_rtcp, *out_reservation_token, *rtcp_s) < 0) { TURN_LOG_FUNC(TURN_LOG_LEVEL_ERROR, "%s: cannot update RTCP map\n", __FUNCTION__); IOA_CLOSE_SOCKET(*rtp_s); if (rtcp_s) IOA_CLOSE_SOCKET(*rtcp_s); return -1; } } ... return 0; }

这样就创建了一个通道，打印的日志如下，

1584: IPv4. Local relay addr: 117.25.xxx.xxx:64425

如果把这个数据给到webrtc的客户端呢？也是通过stun的协议，发到请求的客户端上。

2.匹配通道

两个客户端都建立了连接，在交换信息的时候，我们需要知道谁跟谁是配对的，这样我们可以把流发到对方上，问题还是的从handle_turn_command看起，handle_turn_command接收到了STUN_METHOD_CHANNEL_BIND 绑定通道的命令，这个命令下会获取匹配的信息，下面是具体的流程分析。

讯享网

讯享网static int handle_turn_command(turn_turnserver *server, ts_ur_super_session *ss, ioa_net_data *in_buffer, ioa_network_buffer_handle nbh, int *resp_constructed, int can_resume) { ... case STUN_METHOD_CHANNEL_BIND: handle_turn_channel_bind(server, ss, &tid, resp_constructed, &err_code, &reason, unknown_attrs, &ua_num, in_buffer, nbh); if(server->verbose) { log_method(ss, "CHANNEL_BIND", err_code, reason); } break; case STUN_METHOD_CREATE_PERMISSION: handle_turn_create_permission(server, ss, &tid, resp_constructed, &err_code, &reason, unknown_attrs, &ua_num, in_buffer, nbh); if(server->verbose) { log_method(ss, "CREATE_PERMISSION", err_code, reason); } break; ... return 0; }

接着继续看看handle_turn_channel_bind后面做了什么事情。

static int handle_turn_channel_bind(turn_turnserver *server, ts_ur_super_session *ss, stun_tid *tid, int *resp_constructed, int *err_code, const u08bits reason, u16bits *unknown_attrs, u16bits *ua_num, ioa_net_data *in_buffer, ioa_network_buffer_handle nbh) { ... case STUN_ATTRIBUTE_XOR_PEER_ADDRESS: { stun_attr_get_addr_str(ioa_network_buffer_data(in_buffer->nbh), ioa_network_buffer_get_size(in_buffer->nbh), sar, &peer_addr, NULL); if(!get_relay_socket(a,peer_addr.ss.sa_family)) { *err_code = 443; *reason = (const u08bits *)"Peer Address Family Mismatch (3)"; } if(addr_get_port(&peer_addr) < 1) { *err_code = 400; *reason = (const u08bits *)"Empty port number in channel bind request"; } else { addr_found = 1; } break; } default: if(attr_type>=0x0000 && attr_type<=0x7FFF) unknown_attrs[(*ua_num)++] = nswap16(attr_type); }; sar = stun_attr_get_next_str(ioa_network_buffer_data(in_buffer->nbh), ioa_network_buffer_get_size(in_buffer->nbh), sar); } ... chn = allocation_get_ch_info_by_peer_addr(a, &peer_addr); if(chn) { *err_code = 400; *reason = (const u08bits *)"You cannot use the same peer with different channel number"; } else { if(!good_peer_addr(server,ss->realm_options.name,&peer_addr)) { *err_code = 403; *reason = (const u08bits *) "Forbidden IP"; } else { chn = allocation_get_new_ch_info(a, chnum, &peer_addr); if (!chn) { *err_code = 500; *reason = (const u08bits *) "Cannot find channel data"; } else { tinfo = (turn_permission_info*) (chn->owner); if (!tinfo) { *err_code = 500; *reason = (const u08bits *) "Wrong turn permission info"; } } } } } ... return 0; }

通过STUN_ATTRIBUTE_XOR_PEER_ADDRESS命令，获取到peer_addr 的地址，紧接着good_peer_addr看看是不是被屏蔽的地址，而后把配对的地址放到map中。

讯享网ch_info* allocation_get_new_ch_info(allocation* a, u16bits chnum, ioa_addr* peer_addr) { turn_permission_info* tinfo = get_from_turn_permission_hashtable(&(a->addr_to_perm), peer_addr); if (!tinfo) tinfo = allocation_add_permission(a, peer_addr); ch_info* chn = ch_map_get(&(a->chns), chnum, 1); chn->allocated = 1; chn->chnum = chnum; chn->port = addr_get_port(peer_addr); addr_cpy(&(chn->peer_addr), peer_addr); chn->owner = tinfo; lm_map_put(&(tinfo->chns), (ur_map_key_type) addr_get_port(peer_addr), (ur_map_value_type) chn); return chn; }

用lm_map_put把peer_addr地址放到map中去。

在前面打通了客户到服务器的通道，在通道获取到客户端的数据时，通过read_client_connection获取到客户端的数据，并转发到匹配的端上。

static int read_client_connection(turn_turnserver *server, ts_ur_super_session *ss, ioa_net_data *in_buffer, int can_resume, int count_usage) { ... if(blen<=orig_blen) { ioa_network_buffer_set_size(in_buffer->nbh,blen); rc = write_to_peerchannel(ss, chnum, in_buffer); } if (eve(server->verbose)) { TURN_LOG_FUNC(TURN_LOG_LEVEL_INFO, "%s: wrote to peer %d bytes\n", __FUNCTION__, (int) rc); } FUNCEND; return 0; } ... return -1; }

write_to_peerchannel负责把数据转发到匹配的通道上，跟进去可以看到。

讯享网static int write_to_peerchannel(ts_ur_super_session* ss, u16bits chnum, ioa_net_data *in_buffer) { int rc = 0; if (ss && (in_buffer->recv_ttl!=0)) { allocation* a = get_allocation_ss(ss); if (is_allocation_valid(a)) { ch_info* chn = allocation_get_ch_info(a, chnum); if (!chn) return -1; /* Channel packets are always sent with DF=0: */ set_df_on_ioa_socket(get_relay_socket_ss(ss, chn->peer_addr.ss.sa_family), 0); ioa_network_buffer_handle nbh = in_buffer->nbh; ioa_network_buffer_add_offset_size(in_buffer->nbh, STUN_CHANNEL_HEADER_LENGTH, 0, ioa_network_buffer_get_size(in_buffer->nbh)-STUN_CHANNEL_HEADER_LENGTH); ioa_network_buffer_header_init(nbh); rc = send_data_from_ioa_socket_nbh(get_relay_socket_ss(ss, chn->peer_addr.ss.sa_family), &(chn->peer_addr), nbh, in_buffer->recv_ttl-1, in_buffer->recv_tos, NULL); in_buffer->nbh = NULL; } } return rc; }

allocation_get_ch_info 是用来获取匹配地址的，之前我们把它放到map下了。

ch_info* allocation_get_ch_info(allocation* a, u16bits chnum) { return ch_map_get(&(a->chns), chnum, 0); }

通过send_data_from_ioa_socket_nbh 把数据发到指定的地址上。

讯享网int send_data_from_ioa_socket_nbh(ioa_socket_handle s, ioa_addr* dest_addr, ioa_network_buffer_handle nbh, int ttl, int tos, int *skip) { ... if (s->connected && !(s->parent_s)) { dest_addr = NULL; /* ignore dest_addr */ } else if (!dest_addr) { dest_addr = &(s->remote_addr); } ret = udp_send(s, dest_addr, (s08bits*) ioa_network_buffer_data(nbh),ioa_network_buffer_get_size(nbh)); ... }

这样通过udp_send 把数据发出去。

到这里，两个重大的问题，都得到了答案。

连通了以后，服务器不断的报告数据的信息：

59025: session 0000001: usage: realm=<nort.gov>, username=<xxx>, rp=1020, rb=, sp=1028, sb= 59025: session 0000004: usage: realm=<nort.gov>, username=<xxx>, rp=1027, rb=, sp=1021, sb= 59027: session 0000001: usage: realm=<nort.gov>, username=<xxx>, rp=1020, rb=, sp=1028, sb= 59027: session 0000004: usage: realm=<nort.gov>, username=<xxx>, rp=1028, rb=, sp=1020, sb=

webrtc入门：8.coturn流程

1.创建流通路

2.匹配通道

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