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Explicitly set the max DTLS MTU size #3609

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Explicitly set the max DTLS MTU size #3609

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1324a8c
set the max dtls mtu size to 1350
addisonpolcyn Nov 13, 2025
927c512
Update dtls.c
addisonpolcyn Nov 14, 2025
49bd178
Update dtls.c
addisonpolcyn Nov 14, 2025
0d8ac7d
Merge pull request #1 from addisonpolcyn/set-dtls-max-mtu
addisonpolcyn Nov 14, 2025
75e5e73
Update src/dtls.c
addisonpolcyn Nov 14, 2025
13232d1
Apply suggestions from code review
addisonpolcyn Nov 14, 2025
338a220
Update src/dtls.c
addisonpolcyn Nov 14, 2025
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6 changes: 5 additions & 1 deletion src/dtls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -591,6 +591,10 @@ janus_dtls_srtp *janus_dtls_srtp_create(void *ice_pc, janus_dtls_role role) {
return NULL;
}
SSL_set_ex_data(dtls->ssl, 0, dtls);
// Set the MTU so that we don't send packets that are too large with no
// fragmentation.
SSL_set_mtu(dtls->ssl, janus_dtls_bio_agent_get_mtu());
DTLS_set_link_mtu(dtls->ssl, janus_dtls_bio_agent_get_mtu());
SSL_set_info_callback(dtls->ssl, janus_dtls_callback);
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dtls->read_bio = BIO_new(BIO_s_mem());
if(!dtls->read_bio) {
Expand Down Expand Up @@ -629,7 +633,7 @@ janus_dtls_srtp *janus_dtls_srtp_create(void *ice_pc, janus_dtls_role role) {
int grp_list[1] = { NID_X9_62_prime256v1 };
SSL_set1_groups(dtls->ssl, grp_list, 1);
#endif
const long flags = SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3 | SSL_OP_NO_COMPRESSION | SSL_OP_SINGLE_ECDH_USE;
const long flags = SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3 | SSL_OP_NO_COMPRESSION | SSL_OP_SINGLE_ECDH_USE | SSL_OP_NO_QUERY_MTU;
SSL_set_options(dtls->ssl, flags);
#ifdef HAVE_DTLS_SETTIMEOUT
JANUS_LOG(LOG_VERB, "[%"SCNu64"] Setting DTLS initial timeout: %"SCNu16"ms\n", handle->handle_id, dtls_timeout_base);
Expand Down