FreeCalypso > hg > themwi-system-sw
comparison mgw/gsm2pstn.c @ 103:3b3f07b112f3
mgw: implement GSM to PSTN forwarding
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Mon, 26 Sep 2022 20:46:19 -0800 |
parents | |
children | f062c32a5116 |
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102:d26d97974c8a | 103:3b3f07b112f3 |
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1 /* | |
2 * In this module we implement our RTP gateway function | |
3 * in the GSM to PSTN direction. | |
4 */ | |
5 | |
6 #include <sys/types.h> | |
7 #include <sys/socket.h> | |
8 #include <netinet/in.h> | |
9 #include <stdio.h> | |
10 #include <stdint.h> | |
11 #include <stdlib.h> | |
12 #include <string.h> | |
13 #include <strings.h> | |
14 #include <syslog.h> | |
15 #include <unistd.h> | |
16 #include <gsm.h> /* libgsm dependency */ | |
17 #include "../include/tmgw_ctrl.h" | |
18 #include "../include/tmgw_const.h" | |
19 #include "struct.h" | |
20 #include "select.h" | |
21 #include "int_defs.h" | |
22 | |
23 #define ERR_WRONG_UDP_SRC 0x0001 | |
24 #define ERR_BAD_RTP_PACKET 0x0002 | |
25 #define ERR_SSRC_CHANGE 0x0004 | |
26 #define ERR_SEQ_BREAK 0x0008 | |
27 #define ERR_TSTAMP_BREAK 0x0010 | |
28 | |
29 void | |
30 gsm2pstn_rtp_in(in_fd, ep) | |
31 struct endpoint *ep; | |
32 { | |
33 struct rtp_packet pkt; | |
34 struct sockaddr_in sin_from; | |
35 socklen_t addrlen; | |
36 int16_t seq_delta; | |
37 int32_t ts_delta; | |
38 int16_t pcm_samples[SAMPLES_PER_FRAME]; | |
39 int rc, m_out; | |
40 | |
41 addrlen = sizeof(struct sockaddr_in); | |
42 rc = recvfrom(in_fd, &pkt, sizeof pkt, 0, | |
43 (struct sockaddr *) &sin_from, &addrlen); | |
44 if (rc < 0) | |
45 return; | |
46 if (sin_from.sin_addr.s_addr != ep->rtp_gsm.remote_addr.sin_addr.s_addr | |
47 || sin_from.sin_port != ep->rtp_gsm.remote_addr.sin_port) { | |
48 if (!(ep->g2p_err_flags & ERR_WRONG_UDP_SRC)) { | |
49 syslog(LOG_ERR, | |
50 "GSM RTP ep got UDP packet from wrong source"); | |
51 ep->g2p_err_flags |= ERR_WRONG_UDP_SRC; | |
52 } | |
53 return; | |
54 } | |
55 if (rc != ep->gsm_rtp_pkt_size) { | |
56 bad_rtp_pkt: if (!(ep->g2p_err_flags & ERR_BAD_RTP_PACKET)) { | |
57 syslog(LOG_ERR, "Rx bad RTP packet on GSM side"); | |
58 ep->g2p_err_flags |= ERR_BAD_RTP_PACKET; | |
59 } | |
60 return; | |
61 } | |
62 if (pkt.v_p_x_cc != 0x80) | |
63 goto bad_rtp_pkt; | |
64 if ((pkt.m_pt & 0x7F) != ep->gsm_payload_type) | |
65 goto bad_rtp_pkt; | |
66 if ((pkt.payload[0] & 0xF0) != ep->gsm_payload_magic) | |
67 goto bad_rtp_pkt; | |
68 if (ep->g2p_state && pkt.ssrc != ep->g2p_ssrc) { | |
69 if (!(ep->g2p_err_flags & ERR_SSRC_CHANGE)) { | |
70 syslog(LOG_ERR, "GSM RTP stream changed SSRC"); | |
71 ep->g2p_err_flags |= ERR_SSRC_CHANGE; | |
72 } | |
73 ep->g2p_state = 0; | |
74 } | |
75 if (ep->g2p_state) { | |
76 seq_delta = ntohs(pkt.seq) - ep->g2p_last_seq; | |
77 ts_delta = ntohl(pkt.tstamp) - ep->g2p_last_ts; | |
78 if (seq_delta <= 0) | |
79 return; /* discard old or duplicate */ | |
80 if (seq_delta != 1) { | |
81 if (!(ep->g2p_err_flags & ERR_SEQ_BREAK)) { | |
82 syslog(LOG_ERR, "GSM RTP stream seq break"); | |
83 ep->g2p_err_flags |= ERR_SEQ_BREAK; | |
84 } | |
85 m_out = 1; | |
86 } else { | |
87 if (ts_delta == SAMPLES_PER_FRAME) | |
88 m_out = 0; | |
89 else if (ts_delta > 0 && | |
90 ts_delta % SAMPLES_PER_FRAME == 0) | |
91 m_out = 1; | |
92 else { | |
93 if (!(ep->g2p_err_flags & ERR_TSTAMP_BREAK)) { | |
94 syslog(LOG_ERR, | |
95 "GSM RTP stream tstamp break"); | |
96 ep->g2p_err_flags |= ERR_TSTAMP_BREAK; | |
97 } | |
98 m_out = 1; | |
99 } | |
100 } | |
101 } else | |
102 m_out = 1; | |
103 ep->g2p_state = 1; | |
104 ep->g2p_ssrc = pkt.ssrc; | |
105 ep->g2p_last_ts = ntohl(pkt.tstamp); | |
106 ep->g2p_last_seq = ntohs(pkt.seq); | |
107 /* actual transcoding and forwarding */ | |
108 if (!(ep->fwd_mode & TMGW_FWD_ENABLE_GSM2PSTN)) { | |
109 ep->g2p_drop_flag = 1; | |
110 return; | |
111 } | |
112 if (ep->g2p_drop_flag) { | |
113 ep->g2p_drop_flag = 0; | |
114 m_out = 1; | |
115 } | |
116 switch (ep->gsm_payload_msg_type) { | |
117 case GSM_TCHF_FRAME: | |
118 gsm_decode(ep->gsm_decoder_state, pkt.payload, pcm_samples); | |
119 break; | |
120 } | |
121 pkt.m_pt = ep->pstn_payload_type; | |
122 if (m_out) | |
123 pkt.m_pt |= 0x80; | |
124 pkt.seq = htons(++ep->g2p_out_seq); | |
125 g711_encode_frame(pcm_samples, pkt.payload, ep->pstn_payload_type); | |
126 addrlen = sizeof(struct sockaddr_in); | |
127 sendto(ep->rtp_pstn.rtp_fd, &pkt, RTP_PACKET_SIZE_PSTN, 0, | |
128 (struct sockaddr *) &ep->rtp_pstn.remote_addr, addrlen); | |
129 } | |
130 | |
131 gsm2pstn_init(ep) | |
132 struct endpoint *ep; | |
133 { | |
134 if (ep->gsm_decoder_state) | |
135 return TMGW_RESP_OK; | |
136 switch (ep->gsm_payload_msg_type) { | |
137 case GSM_TCHF_FRAME: | |
138 ep->gsm_decoder_state = gsm_create(); | |
139 if (!ep->gsm_decoder_state) | |
140 return TMGW_RESP_ERR_RSRC; | |
141 break; | |
142 } | |
143 select_handlers[ep->rtp_gsm.rtp_fd] = gsm2pstn_rtp_in; | |
144 return TMGW_RESP_OK; | |
145 } |