diff --git a/daemon/call_interfaces.c b/daemon/call_interfaces.c
index 455c06c39..2c5c93be0 100644
--- a/daemon/call_interfaces.c
+++ b/daemon/call_interfaces.c
@@ -1442,6 +1442,7 @@ void call_ng_flags_init(sdp_ng_flags *out, enum ng_opmode opmode) {
out->frequencies = g_array_new(false, false, sizeof(int));
for (int i = 0; i < __MT_MAX; ++i)
out->sdp_media_remove[i] = false;
+ out->t38_version = -1;
}
static void call_ng_direction_flag_iter(str *s, unsigned int i, helper_arg arg) {
@@ -2105,6 +2106,17 @@ void call_ng_main_flags(const ng_parser_t *parser, str *key, parser_arg value, h
case CSH_LOOKUP("t.38"):
call_ng_flags_str_list(parser, value, ng_t38_option, out);
break;
+
+ case CSH_LOOKUP("T38-version"):
+ case CSH_LOOKUP("T.38-version"):
+ case CSH_LOOKUP("t38-version"):
+ case CSH_LOOKUP("t.38-version"):
+ case CSH_LOOKUP("T38 version"):
+ case CSH_LOOKUP("T.38 version"):
+ case CSH_LOOKUP("t38 version"):
+ case CSH_LOOKUP("t.38 version"):
+ out->t38_version = parser->get_int_str(value, out->t38_version);
+ break;
#endif
case CSH_LOOKUP("template"):;
str *tplate = t_hash_table_lookup(rtpe_signalling_templates, &s);
diff --git a/daemon/codec.c b/daemon/codec.c
index ce4853c2a..4ff9063da 100644
--- a/daemon/codec.c
+++ b/daemon/codec.c
@@ -876,6 +876,10 @@ static void __t38_options_from_flags(struct t38_options *t_opts, const sdp_ng_fl
t38_opt(no_v29);
t38_opt(no_v34);
t38_opt(no_iaf);
+#undef t38_opt
+
+ if (flags && flags->t38_version >= 0)
+ t_opts->version = flags->t38_version;
}
static void __check_t38_gateway(struct call_media *pcm_media, struct call_media *t38_media,
@@ -891,6 +895,7 @@ static void __check_t38_gateway(struct call_media *pcm_media, struct call_media
t_opts.fec_span = 3;
t_opts.max_ec_entries = 3;
}
+
__t38_options_from_flags(&t_opts, flags);
MEDIA_SET(pcm_media, GENERATOR);
diff --git a/docs/ng_control_protocol.md b/docs/ng_control_protocol.md
index 66ea3f4c2..868b814c9 100644
--- a/docs/ng_control_protocol.md
+++ b/docs/ng_control_protocol.md
@@ -860,6 +860,14 @@ Optionally included keys are:
Use UDPTL FEC instead of redundancy. Only useful with `T.38=force` as
it's a negotiated parameter.
+* `T.38 version`
+
+ Sets the T.38 version number to use for the T.38 gateway. The default is
+ version zero, or to go along with what has been advertised in the SDP if
+ responding to a received T.38 offer. Overriding the version to zero
+ regardless of what has been advertised in the SDP can solve T.38 gateway
+ problems against certain endpoints.
+
* `volume`
Sets the tone volume for `DTMF-security` modes `tone`, `zero, `DTMF`,
diff --git a/include/call_interfaces.h b/include/call_interfaces.h
index 6b614cbe2..6063e45b3 100644
--- a/include/call_interfaces.h
+++ b/include/call_interfaces.h
@@ -154,6 +154,7 @@ struct sdp_ng_flags {
str vsc_pause_rec;
str vsc_pause_resume_rec;
str vsc_start_pause_resume_rec;
+ int t38_version;
#define X(x) str_q x;
RTPE_NG_FLAGS_STR_Q_PARAMS
diff --git a/t/auto-daemon-tests-t38.pl b/t/auto-daemon-tests-t38.pl
index a740d6f4b..cd3bdf784 100755
--- a/t/auto-daemon-tests-t38.pl
+++ b/t/auto-daemon-tests-t38.pl
@@ -681,6 +681,114 @@ t38_gw_test('FEC span 5',
+new_call;
+
+offer('override T.38 version control', { 'T.38' => [ 'decode' ] }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=image 4000 udptl t38
+c=IN IP4 198.51.100.1
+a=sendrecv
+a=T38FaxVersion:1
+a=T38MaxBitRate:14400
+a=T38FaxRateManagement:transferredTCF
+a=T38FaxMaxBuffer:262
+a=T38FaxMaxDatagram:300
+a=T38FaxUdpEC:t38UDPRedundancy
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 0 8
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=rtpmap:8 PCMA/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+answer('override T.38 version control', { }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 4002 RTP/AVP 8
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=image PORT udptl t38
+c=IN IP4 203.0.113.1
+a=T38FaxVersion:1
+a=T38MaxBitRate:14400
+a=T38FaxRateManagement:transferredTCF
+a=T38FaxMaxBuffer:1800
+a=T38FaxMaxDatagram:512
+a=T38FaxUdpEC:t38UDPRedundancy
+a=sendrecv
+SDP
+
+
+new_call;
+
+offer('override T.38 version', { 'T.38' => [ 'decode' ], 'T.38 version' => 0 }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=image 4000 udptl t38
+c=IN IP4 198.51.100.1
+a=sendrecv
+a=T38FaxVersion:1
+a=T38MaxBitRate:14400
+a=T38FaxRateManagement:transferredTCF
+a=T38FaxMaxBuffer:262
+a=T38FaxMaxDatagram:300
+a=T38FaxUdpEC:t38UDPRedundancy
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 0 8
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=rtpmap:8 PCMA/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+answer('override T.38 version', { }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 4002 RTP/AVP 8
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=image PORT udptl t38
+c=IN IP4 203.0.113.1
+a=T38FaxVersion:0
+a=T38MaxBitRate:14400
+a=T38FaxRateManagement:transferredTCF
+a=T38FaxMaxBuffer:1800
+a=T38FaxMaxDatagram:512
+a=T38FaxUdpEC:t38UDPRedundancy
+a=sendrecv
+SDP
+
+
# XXX packet loss tests
# XXX tests of different SDP options