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Diffstat (limited to 'PICA_media.h')
| -rw-r--r-- | PICA_media.h | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/PICA_media.h b/PICA_media.h new file mode 100644 index 0000000..971b918 --- /dev/null +++ b/PICA_media.h @@ -0,0 +1,177 @@ +/* + (c) Copyright 2012 - 2026 Anton Sviridenko + https://picapica.im + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, version 3. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. +*/ + +/* mediac2c connections - call media over UDP, protected by DTLS. + * + * A mediac2c connection exists only while a call is in progress and only + * between two clients that already have an established directc2c connection. + * It reuses that connection's address and port number with UDP instead of + * TCP, so nothing has to be announced or negotiated over the c2c connection: + * the client that made the outgoing directc2c connection is the DTLS client, + * the one that accepted it is the DTLS server. + * + * Media packets are sent over this connection whenever it is established and + * over the c2c/directc2c connection otherwise; the receiving side accepts + * them over either transport at any time, so there is no moment where the + * media stops while the transport changes. + */ + +#ifndef PICA_MEDIA_H +#define PICA_MEDIA_H + +#include "PICA_client.h" + +/* Link MTU assumed for a mediac2c connection until path MTU discovery + * (RFC 8899) is implemented. 1200 octets is the value QUIC uses as the size + * every path is expected to carry. + */ +#define PICA_MEDIA_LINK_MTU 1200 +/* IPv4 + UDP headers */ +#define PICA_MEDIA_IPUDP_OVERHEAD 28 + +/* Amount of media data that certainly fits into one datagram of a mediac2c + * connection: the assumed link MTU less a generous allowance for the IP, UDP, + * DTLS record and protocol message headers, whose exact sizes depend on the + * ciphersuite that ends up being negotiated. + * It lets the media be produced in datagram sized pieces from the start of a + * call, before it is known whether a media connection will come up at all, + * rather than having to change size in the middle of one. + */ +#define PICA_MEDIA_SAFE_PAYLOAD (PICA_MEDIA_LINK_MTU - 100) + +/* How long a call keeps trying to bring the media connection up before + * giving up and carrying the media over the c2c connection for the rest of + * the call, in seconds. + */ +#define PICA_MEDIA_HANDSHAKE_TIMEOUT 10 + +/* An established media connection with no datagram received for this many + * seconds is considered broken; media falls back to the c2c connection. + */ +#define PICA_MEDIA_SILENCE_TIMEOUT 10 + +/* Ping is sent over an established media connection after this many seconds + * without anything being sent, to hold NAT and firewall state open. + */ +#define PICA_MEDIA_KEEPALIVE_INTERVAL 4 + +#define PICA_MEDIA_READBUFSIZE 4096 + +/* transport of the media packets of a call, reported by call_media_transport_cb */ +#define PICA_CALL_TRANSPORT_C2C 0 +#define PICA_CALL_TRANSPORT_MEDIAC2C 1 + +enum PICA_media_state +{ + PICA_MEDIA_STATE_NEW = 0, + /* DTLS server role, socket bound, waiting for the first datagram */ + PICA_MEDIA_STATE_LISTENING, + PICA_MEDIA_STATE_HANDSHAKE, + PICA_MEDIA_STATE_ACTIVE, + PICA_MEDIA_STATE_FAILED +}; + +struct PICA_media_listener +{ + const struct PICA_acc *acc; + SOCKET sck; + int public_port; + int local_port; + + /* The media connection currently using this listener's socket, if any. + * Only one call can be in progress at a time, so there is at most one. + */ + struct PICA_media_channel *channel; +}; + +struct PICA_media_channel +{ + struct PICA_c2c *c2c; + /* set when this side has the DTLS server role */ + struct PICA_media_listener *listener; + + SOCKET sck; + /* 0 when sck belongs to the listener and must not be closed with the + * channel + */ + int owns_sck; + struct sockaddr_in peer_addr; + + SSL *ssl; + X509 *peer_cert; + int is_dtls_client; + + enum PICA_media_state state; + time_t started; + time_t last_rx; + time_t last_tx; + + unsigned int max_payload; + + unsigned char read_buf[PICA_MEDIA_READBUFSIZE]; + unsigned int read_pos; +}; + +#ifdef __cplusplus +extern "C" { +#endif + +/* implemented in PICA_media.c */ + +int PICA_media_listener_new(const struct PICA_acc *acc, int public_port, int local_port, + struct PICA_media_listener **ml); +void PICA_media_listener_close(struct PICA_media_listener *ml); + +/** + * Brings up a media connection for a call that has just become active. + * Does nothing if the preconditions (an established directc2c connection, + * and a media listener on the accepting side) are not met - the media then + * stays on the c2c connection. + */ +void PICA_media_start(struct PICA_c2c *c2c); +void PICA_media_close(struct PICA_c2c *c2c); + +int PICA_media_is_active(const struct PICA_c2c *c2c); +/** + * Largest amount of data one media packet can carry over this c2c connection, + * i.e. what has to fit into one datagram once a media connection is up. + */ +unsigned int PICA_media_max_payload(const struct PICA_c2c *c2c); + +/** + * Sends one already formatted protocol message over the media connection. + * The message is dropped, and PICA_OK returned, if the send would block - + * for real time media that is the wanted behaviour. + */ +int PICA_media_send(struct PICA_c2c *c2c, const unsigned char *buf, unsigned int len); + +void PICA_media_fdset(struct PICA_c2n *c2n, fd_set *rfds, int *nfds); +void PICA_media_process(struct PICA_c2n *c2n, fd_set *rfds); + +/* implemented in PICA_client.c, used by PICA_media.c */ + +int PICA_verify_callback(int preverify_ok, X509_STORE_CTX *ctx); +int PICA_verify_peer_cert_common(X509 **peer_cert, SSL *ssl, const unsigned char *peer_id); +unsigned int PICA_media_process_messages(unsigned char *buf, unsigned int *read_pos, struct PICA_c2c *c2c); +void PICA_media_transport_changed(struct PICA_c2c *c2c, int transport, const char *ciphersuitename); +int PICA_media_send_ping(struct PICA_c2c *c2c, int reply); + +#ifdef __cplusplus +} +#endif + +#endif |