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Feature: Implement ICE lite support and consent freshness #25

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Feature: Implement ICE lite support and consent freshness #25

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70 changes: 67 additions & 3 deletions libavformat/whip.c
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,7 @@
#include "network.h"
#include "srtp.h"
#include "tls.h"

#include <errno.h>
/**
* Maximum size limit of a Session Description Protocol (SDP),
* be it an offer or answer.
Expand Down Expand Up @@ -143,6 +143,12 @@
#define WHIP_RTCP_PT_START 192
#define WHIP_RTCP_PT_END 223

/**
* Consent-freshness constants �����������������������������������������
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Special chars?

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@murillo128 same question as #23 (comment)

*/
#define WHIP_CONSENT_DEF_INTERVAL 15000 /* ms � RFC 7675 default */
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#define WHIP_CONSENT_MAX_FAILURES 3

/**
* In the case of ICE-LITE, these fields are not used; instead, they are defined
* as constant values.
Expand All @@ -156,9 +162,11 @@
/* STUN Attribute, comprehension-required range (0x0000-0x7FFF) */
enum STUNAttr {
STUN_ATTR_USERNAME = 0x0006, /// shared secret response/bind request
STUN_ATTR_PRIORITY = 0x0024, /// ICE controlling/controlled
STUN_ATTR_USE_CANDIDATE = 0x0025, /// bind request
STUN_ATTR_MESSAGE_INTEGRITY = 0x0008, /// bind request/response
STUN_ATTR_FINGERPRINT = 0x8028, /// rfc5389
STUN_ATTR_ICE_CONTROLLING = 0x802A, /// full agent talking to ice-lite
};

enum WHIPState {
Expand Down Expand Up @@ -303,6 +311,15 @@ typedef struct WHIPContext {
/* The certificate and private key used for DTLS handshake. */
char* cert_file;
char* key_file;

/* Consent-freshness state */
int consent_interval;
int64_t last_consent_tx;
int consent_failures;

/* ICE-lite support */
int ice_lite_remote;
uint64_t ice_tie_breaker; /* random 64-bit, for ICE-CONTROLLING */
} WHIPContext;

/**
Expand Down Expand Up @@ -412,6 +429,15 @@ static av_cold int initialize(AVFormatContext *s)
seed = av_get_random_seed();
av_lfg_init(&whip->rnd, seed);

/* 64-bit tie-breaker for ICE-CONTROLLING (RFC 8445 6.1.1) */
whip->ice_tie_breaker = ((uint64_t)av_lfg_get(&whip->rnd) << 32) | (uint64_t)av_lfg_get(&whip->rnd);

/* Initialise consent-freshness timers */
if (whip->consent_interval <= 0)
whip->consent_interval = WHIP_CONSENT_DEF_INTERVAL;
whip->last_consent_tx = av_gettime();
whip->consent_failures = 0;

if (whip->pkt_size < ideal_pkt_size)
av_log(whip, AV_LOG_WARNING, "WHIP: pkt_size=%d(<%d) is too small, may cause packet loss\n",
whip->pkt_size, ideal_pkt_size);
Expand Down Expand Up @@ -894,6 +920,8 @@ static int parse_answer(AVFormatContext *s)
goto end;
}
}
} else if (av_strstart(line, "a=ice-lite", NULL)) {
whip->ice_lite_remote = 1;
}
}

Expand Down Expand Up @@ -985,6 +1013,22 @@ static int ice_create_request(AVFormatContext *s, uint8_t *buf, int buf_size, in
avio_wb16(pb, STUN_ATTR_USE_CANDIDATE); /* attribute type use-candidate */
avio_wb16(pb, 0); /* size of use-candidate */

/**
* For ICE-lite peers we are *always* the controlling agent (RFC 8445 6.1.3.1).
* Add PRIORITY + ICE-CONTROLLING attributes.
*/
if (whip->ice_lite_remote) {
/* we are controlling, use host-candidate priority 126 << 24 | 65535 << 8 | 255 = 2130706431 */
avio_wb16(pb, STUN_ATTR_PRIORITY);
avio_wb16(pb, 4);
avio_wb32(pb, 2130706431);

avio_wb16(pb, STUN_ATTR_ICE_CONTROLLING);
avio_wb16(pb, 8);
avio_wb32(pb, (uint32_t)(whip->ice_tie_breaker >> 32));
avio_wb32(pb, (uint32_t)(whip->ice_tie_breaker & 0xffffffff));
}

/* Build and update message integrity */
avio_wb16(pb, STUN_ATTR_MESSAGE_INTEGRITY); /* attribute type message integrity */
avio_wb16(pb, 20); /* size of message integrity */
Expand Down Expand Up @@ -1775,14 +1819,27 @@ static int whip_write_packet(AVFormatContext *s, AVPacket *pkt)
AVStream *st = s->streams[pkt->stream_index];
AVFormatContext *rtp_ctx = st->priv_data;

/* TODO: Send binding request every 1s as WebRTC heartbeat. */
/* Periodic consent-freshness STUN Binding Request */
int64_t now = av_gettime();
if (now - whip->last_consent_tx >= (int64_t)whip->consent_interval * 1000) {
int req_sz;
if (ice_create_request(s, whip->buf, sizeof(whip->buf), &req_sz) >= 0 && ffurl_write(whip->udp, whip->buf, req_sz) == req_sz) {
whip->consent_failures++;
whip->last_consent_tx = now;
av_log(whip, AV_LOG_VERBOSE, "WHIP: consent-freshness request %d sent\n", whip->consent_failures);
}
}

/**
* Receive packets from the server such as ICE binding requests, DTLS messages,
* and RTCP like PLI requests, then respond to them.
*/
ret = ffurl_read(whip->udp, whip->buf, sizeof(whip->buf));
if (ret > 0) {
if (ice_is_binding_response(whip->buf, ret)) {
whip->consent_failures = 0;
av_log(whip, AV_LOG_VERBOSE, "WHIP: consent-freshness response received, counter reset\n");
}
if (is_dtls_packet(whip->buf, ret)) {
if ((ret = ffurl_write(whip->dtls_uc, whip->buf, ret)) < 0) {
av_log(whip, AV_LOG_ERROR, "WHIP: Failed to handle DTLS message\n");
Expand All @@ -1793,6 +1850,12 @@ static int whip_write_packet(AVFormatContext *s, AVPacket *pkt)
av_log(whip, AV_LOG_ERROR, "WHIP: Failed to read from UDP socket\n");
goto end;
}
/* Check consent freshness consecutive failures */
if (whip->consent_failures >= WHIP_CONSENT_MAX_FAILURES) {
av_log(whip, AV_LOG_ERROR, "WHIP: No consent-freshness response after %d attempts, closing\n", WHIP_CONSENT_MAX_FAILURES);
ret = AVERROR(EHOSTUNREACH);
goto end;
}

if (whip->h264_annexb_insert_sps_pps && st->codecpar->codec_id == AV_CODEC_ID_H264) {
if ((ret = h264_annexb_insert_sps_pps(s, pkt)) < 0) {
Expand Down Expand Up @@ -1891,7 +1954,8 @@ static const AVOption options[] = {
{ "pkt_size", "The maximum size, in bytes, of RTP packets that send out", OFFSET(pkt_size), AV_OPT_TYPE_INT, { .i64 = 1200 }, -1, INT_MAX, DEC },
{ "authorization", "The optional Bearer token for WHIP Authorization", OFFSET(authorization), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, DEC },
{ "cert_file", "The optional certificate file path for DTLS", OFFSET(cert_file), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, DEC },
{ "key_file", "The optional private key file path for DTLS", OFFSET(key_file), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, DEC },
{ "key_file", "The optional private key file path for DTLS", OFFSET(key_file), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, DEC },
{ "consent_interval", "STUN consent refresh interval in ms (RFC 7675)", OFFSET(consent_interval), AV_OPT_TYPE_INT, { .i64 = WHIP_CONSENT_DEF_INTERVAL }, 5000, 30000, DEC },
{ NULL },
};

Expand Down