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avformat: Add IPFS protocol support.

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This patch adds support for:
- ffplay ipfs://<cid>
- ffplay ipns://<cid>

IPFS data can be played from so called "ipfs gateways".
A gateway is essentially a webserver that gives access to the
distributed IPFS network.

This protocol support (ipfs and ipns) therefore translates
ipfs:// and ipns:// to a http:// url. This resulting url is
then handled by the http protocol. It could also be https
depending on the gateway provided.

To use this protocol, a gateway must be provided.
If you do nothing it will try to find it in your
$HOME/.ipfs/gateway file. The ways to set it manually are:
1. Define a -gateway <url> to the gateway.
2. Define $IPFS_GATEWAY with the full http link to the gateway.
3. Define $IPFS_PATH and point it to the IPFS data path.
4. Have IPFS running in your local user folder (under $HOME/.ipfs).

Signed-off-by: Mark Gaiser <markg85@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Mark Gaiser 2022-04-06 14:00:56 +02:00 committed by Michael Niedermayer
parent c2351d5a53
commit f889837e00
6 changed files with 378 additions and 1 deletions
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2
configure vendored
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@ -3581,6 +3581,8 @@ udp_protocol_select="network"
udplite_protocol_select="network"
unix_protocol_deps="sys_un_h"
unix_protocol_select="network"
ipfs_protocol_select="https_protocol"
ipns_protocol_select="https_protocol"
# external library protocols
libamqp_protocol_deps="librabbitmq"

30
doc/protocols.texi
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@ -2025,5 +2025,35 @@ decoding errors.
@end table
@section ipfs
InterPlanetary File System (IPFS) protocol support. One can access files stored
on the IPFS network through so called gateways. Those are http(s) endpoints.
This protocol wraps the IPFS native protocols (ipfs:// and ipns://) to be send
to such a gateway. Users can (and should) host their own node which means this
protocol will use your local gateway to access files on the IPFS network.
If a user doesn't have a node of their own then the public gateway dweb.link is
used by default.
You can use this protocol in 2 ways. Using IPFS:
@example
ffplay ipfs://QmbGtJg23skhvFmu9mJiePVByhfzu5rwo74MEkVDYAmF5T
@end example
Or the IPNS protocol (IPNS is mutable IPFS):
@example
ffplay ipns://QmbGtJg23skhvFmu9mJiePVByhfzu5rwo74MEkVDYAmF5T
@end example
You can also change the gateway to be used:
@table @option
@item gateway
Defines the gateway to use. When nothing is provided the protocol will first try
your local gateway. If that fails dweb.link will be used.
@end table
@c man end PROTOCOLS

2
libavformat/Makefile
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@ -660,6 +660,8 @@ OBJS-$(CONFIG_SRTP_PROTOCOL) += srtpproto.o srtp.o
OBJS-$(CONFIG_SUBFILE_PROTOCOL) += subfile.o
OBJS-$(CONFIG_TEE_PROTOCOL) += teeproto.o tee_common.o
OBJS-$(CONFIG_TCP_PROTOCOL) += tcp.o
OBJS-$(CONFIG_IPFS_PROTOCOL) += ipfsgateway.o
OBJS-$(CONFIG_IPNS_PROTOCOL) += ipfsgateway.o
TLS-OBJS-$(CONFIG_GNUTLS) += tls_gnutls.o
TLS-OBJS-$(CONFIG_LIBTLS) += tls_libtls.o
TLS-OBJS-$(CONFIG_MBEDTLS) += tls_mbedtls.o

341
libavformat/ipfsgateway.c Normal file
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@ -0,0 +1,341 @@
/*
* IPFS and IPNS protocol support through IPFS Gateway.
* Copyright (c) 2022 Mark Gaiser
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavutil/avstring.h"
#include "libavutil/opt.h"
#include <sys/stat.h>
#include "os_support.h"
#include "url.h"
typedef struct IPFSGatewayContext {
AVClass *class;
URLContext *inner;
// Is filled by the -gateway argument and not changed after.
char *gateway;
// If the above gateway is non null, it will be copied into this buffer.
// Else this buffer will contain the auto detected gateway.
// In either case, the gateway to use will be in this buffer.
char gateway_buffer[PATH_MAX];
} IPFSGatewayContext;
// A best-effort way to find the IPFS gateway.
// Only the most appropiate gateway is set. It's not actually requested
// (http call) to prevent a potential slowdown in startup. A potential timeout
// is handled by the HTTP protocol.
static int populate_ipfs_gateway(URLContext *h)
{
IPFSGatewayContext *c = h->priv_data;
char ipfs_full_data_folder[PATH_MAX];
char ipfs_gateway_file[PATH_MAX];
struct stat st;
int stat_ret = 0;
int ret = AVERROR(EINVAL);
FILE *gateway_file = NULL;
// Test $IPFS_GATEWAY.
if (getenv("IPFS_GATEWAY") != NULL) {
if (snprintf(c->gateway_buffer, sizeof(c->gateway_buffer), "%s",
getenv("IPFS_GATEWAY"))
>= sizeof(c->gateway_buffer)) {
av_log(h, AV_LOG_WARNING,
"The IPFS_GATEWAY environment variable "
"exceeds the maximum length. "
"We allow a max of %zu characters\n",
sizeof(c->gateway_buffer));
ret = AVERROR(EINVAL);
goto err;
}
ret = 1;
goto err;
} else
av_log(h, AV_LOG_DEBUG, "$IPFS_GATEWAY is empty.\n");
// We need to know the IPFS folder to - eventually - read the contents of
// the "gateway" file which would tell us the gateway to use.
if (getenv("IPFS_PATH") == NULL) {
av_log(h, AV_LOG_DEBUG, "$IPFS_PATH is empty.\n");
// Try via the home folder.
if (getenv("HOME") == NULL) {
av_log(h, AV_LOG_WARNING, "$HOME appears to be empty.\n");
ret = AVERROR(EINVAL);
goto err;
}
// Verify the composed path fits.
if (snprintf(ipfs_full_data_folder, sizeof(ipfs_full_data_folder),
"%s/.ipfs/", getenv("HOME"))
>= sizeof(ipfs_full_data_folder)) {
av_log(h, AV_LOG_WARNING,
"The IPFS data path exceeds the "
"max path length (%zu)\n",
sizeof(ipfs_full_data_folder));
ret = AVERROR(EINVAL);
goto err;
}
// Stat the folder.
// It should exist in a default IPFS setup when run as local user.
stat_ret = stat(ipfs_full_data_folder, &st);
if (stat_ret < 0) {
av_log(h, AV_LOG_INFO,
"Unable to find IPFS folder. We tried:\n"
"- $IPFS_PATH, which was empty.\n"
"- $HOME/.ipfs (full uri: %s) which doesn't exist.\n",
ipfs_full_data_folder);
ret = AVERROR(ENOENT);
goto err;
}
} else {
if (snprintf(ipfs_full_data_folder, sizeof(ipfs_full_data_folder), "%s",
getenv("IPFS_PATH"))
>= sizeof(ipfs_full_data_folder)) {
av_log(h, AV_LOG_WARNING,
"The IPFS_PATH environment variable "
"exceeds the maximum length. "
"We allow a max of %zu characters\n",
sizeof(c->gateway_buffer));
ret = AVERROR(EINVAL);
goto err;
}
}
// Copy the fully composed gateway path into ipfs_gateway_file.
if (snprintf(ipfs_gateway_file, sizeof(ipfs_gateway_file), "%sgateway",
ipfs_full_data_folder)
>= sizeof(ipfs_gateway_file)) {
av_log(h, AV_LOG_WARNING,
"The IPFS gateway file path exceeds "
"the max path length (%zu)\n",
sizeof(ipfs_gateway_file));
ret = AVERROR(ENOENT);
goto err;
}
// Get the contents of the gateway file.
gateway_file = av_fopen_utf8(ipfs_gateway_file, "r");
if (!gateway_file) {
av_log(h, AV_LOG_WARNING,
"The IPFS gateway file (full uri: %s) doesn't exist. "
"Is the gateway enabled?\n",
ipfs_gateway_file);
ret = AVERROR(ENOENT);
goto err;
}
// Read a single line (fgets stops at new line mark).
if (!fgets(c->gateway_buffer, sizeof(c->gateway_buffer) - 1, gateway_file)) {
av_log(h, AV_LOG_WARNING, "Unable to read from file (full uri: %s).\n",
ipfs_gateway_file);
ret = AVERROR(ENOENT);
goto err;
}
// Replace first occurence of end of line with \0
c->gateway_buffer[strcspn(c->gateway_buffer, "\r\n")] = 0;
// If strlen finds anything longer then 0 characters then we have a
// potential gateway url.
if (*c->gateway_buffer == '\0') {
av_log(h, AV_LOG_WARNING,
"The IPFS gateway file (full uri: %s) appears to be empty. "
"Is the gateway started?\n",
ipfs_gateway_file);
ret = AVERROR(EILSEQ);
goto err;
} else {
// We're done, the c->gateway_buffer has something that looks valid.
ret = 1;
goto err;
}
err:
if (gateway_file)
fclose(gateway_file);
return ret;
}
static int translate_ipfs_to_http(URLContext *h, const char *uri, int flags, AVDictionary **options)
{
const char *ipfs_cid;
char *fulluri = NULL;
int ret;
IPFSGatewayContext *c = h->priv_data;
// Test for ipfs://, ipfs:, ipns:// and ipns:. This prefix is stripped from
// the string leaving just the CID in ipfs_cid.
int is_ipfs = av_stristart(uri, "ipfs://", &ipfs_cid);
int is_ipns = av_stristart(uri, "ipns://", &ipfs_cid);
// We must have either ipns or ipfs.
if (!is_ipfs && !is_ipns) {
ret = AVERROR(EINVAL);
av_log(h, AV_LOG_WARNING, "Unsupported url %s\n", uri);
goto err;
}
// If the CID has a length greater then 0 then we assume we have a proper working one.
// It could still be wrong but in that case the gateway should save us and
// ruturn a 403 error. The http protocol handles this.
if (strlen(ipfs_cid) < 1) {
av_log(h, AV_LOG_WARNING, "A CID must be provided.\n");
ret = AVERROR(EILSEQ);
goto err;
}
// Populate c->gateway_buffer with whatever is in c->gateway
if (c->gateway != NULL) {
if (snprintf(c->gateway_buffer, sizeof(c->gateway_buffer), "%s",
c->gateway)
>= sizeof(c->gateway_buffer)) {
av_log(h, AV_LOG_WARNING,
"The -gateway parameter is too long. "
"We allow a max of %zu characters\n",
sizeof(c->gateway_buffer));
ret = AVERROR(EINVAL);
goto err;
}
} else {
// Populate the IPFS gateway if we have any.
// If not, inform the user how to properly set one.
ret = populate_ipfs_gateway(h);
if (ret < 1) {
// We fallback on dweb.link (managed by Protocol Labs).
snprintf(c->gateway_buffer, sizeof(c->gateway_buffer), "https://dweb.link");
av_log(h, AV_LOG_WARNING,
"IPFS does not appear to be running. "
"You’re now using the public gateway at dweb.link.\n");
av_log(h, AV_LOG_INFO,
"Installing IPFS locally is recommended to "
"improve performance and reliability, "
"and not share all your activity with a single IPFS gateway.\n"
"There are multiple options to define this gateway.\n"
"1. Call ffmpeg with a gateway param, "
"without a trailing slash: -gateway <url>.\n"
"2. Define an $IPFS_GATEWAY environment variable with the "
"full HTTP URL to the gateway "
"without trailing forward slash.\n"
"3. Define an $IPFS_PATH environment variable "
"and point it to the IPFS data path "
"- this is typically ~/.ipfs\n");
}
}
// Test if the gateway starts with either http:// or https://
if (av_stristart(c->gateway_buffer, "http://", NULL) == 0
&& av_stristart(c->gateway_buffer, "https://", NULL) == 0) {
av_log(h, AV_LOG_WARNING,
"The gateway URL didn't start with http:// or "
"https:// and is therefore invalid.\n");
ret = AVERROR(EILSEQ);
goto err;
}
// Concatenate the url.
// This ends up with something like: http://localhost:8080/ipfs/Qm.....
// The format of "%s%s%s%s" is the following:
// 1st %s = The gateway.
// 2nd %s = If the gateway didn't end in a slash, add a "/". Otherwise it's an empty string
// 3rd %s = Either ipns/ or ipfs/.
// 4th %s = The IPFS CID (Qm..., bafy..., ...).
fulluri = av_asprintf("%s%s%s%s",
c->gateway_buffer,
(c->gateway_buffer[strlen(c->gateway_buffer) - 1] == '/') ? "" : "/",
(is_ipns) ? "ipns/" : "ipfs/",
ipfs_cid);
if (!fulluri) {
av_log(h, AV_LOG_ERROR, "Failed to compose the URL\n");
ret = AVERROR(ENOMEM);
goto err;
}
// Pass the URL back to FFMpeg's protocol handler.
ret = ffurl_open_whitelist(&c->inner, fulluri, flags,
&h->interrupt_callback, options,
h->protocol_whitelist,
h->protocol_blacklist, h);
if (ret < 0) {
av_log(h, AV_LOG_WARNING, "Unable to open resource: %s\n", fulluri);
goto err;
}
err:
av_free(fulluri);
return ret;
}
static int ipfs_read(URLContext *h, unsigned char *buf, int size)
{
IPFSGatewayContext *c = h->priv_data;
return ffurl_read(c->inner, buf, size);
}
static int64_t ipfs_seek(URLContext *h, int64_t pos, int whence)
{
IPFSGatewayContext *c = h->priv_data;
return ffurl_seek(c->inner, pos, whence);
}
static int ipfs_close(URLContext *h)
{
IPFSGatewayContext *c = h->priv_data;
return ffurl_closep(&c->inner);
}
#define OFFSET(x) offsetof(IPFSGatewayContext, x)
static const AVOption options[] = {
{"gateway", "The gateway to ask for IPFS data.", OFFSET(gateway), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, AV_OPT_FLAG_DECODING_PARAM},
{NULL},
};
static const AVClass ipfs_context_class = {
.class_name = "IPFS",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
};
const URLProtocol ff_ipfs_protocol = {
.name = "ipfs",
.url_open2 = translate_ipfs_to_http,
.url_read = ipfs_read,
.url_seek = ipfs_seek,
.url_close = ipfs_close,
.priv_data_size = sizeof(IPFSGatewayContext),
.priv_data_class = &ipfs_context_class,
};
const URLProtocol ff_ipns_protocol = {
.name = "ipns",
.url_open2 = translate_ipfs_to_http,
.url_read = ipfs_read,
.url_seek = ipfs_seek,
.url_close = ipfs_close,
.priv_data_size = sizeof(IPFSGatewayContext),
.priv_data_class = &ipfs_context_class,
};

2
libavformat/protocols.c
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@ -71,6 +71,8 @@ extern const URLProtocol ff_libsrt_protocol;
extern const URLProtocol ff_libssh_protocol;
extern const URLProtocol ff_libsmbclient_protocol;
extern const URLProtocol ff_libzmq_protocol;
extern const URLProtocol ff_ipfs_protocol;
extern const URLProtocol ff_ipns_protocol;
#include "libavformat/protocol_list.c"

2
libavformat/version.h
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@ -31,7 +31,7 @@
#include "version_major.h"
#define LIBAVFORMAT_VERSION_MINOR 21
#define LIBAVFORMAT_VERSION_MINOR 22
#define LIBAVFORMAT_VERSION_MICRO 100
#define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \