[FFmpeg-devel] [PATCH v2 0/1] Add IPFS protocol support.

[FFmpeg-devel] [PATCH v2 0/1] Add IPFS protocol support.

[Mark Gaiser]

Hi,

This patch series adds support for IPFS.
V3:
- A lot of style changes
- Made url checks a lot more strict
- av_asprintf leak fixes
- So many changes that a diff to v2 is again not sensible.
V2:
- Squashed and changed so much that a diff to v1 was not sensible.

The following is a short summary. In the IPFS ecosystem you access it's content
by a "Content IDentifier" (CID). This CID is, in simplified terms, a hash of 
the content. IPFS itself is a distributed network where any user can run a node
to be part of the network and access files by their CID. If any reachable node 
within that network has the CID, you can get it.

IPFS (as a technology) has two protocols, ipfs and ipns.
The ipfs protocol is the immutable way to access content.
The ipns protocol is a mutable layer on top of it. It's essentially a new CID 
that points to a ipfs CID. This "pointer" if you will can be changed to point 
to something else.
Much more information on how this technology works can be found here [1].

This patch series allows to interact natively with IPFS. That means being able
to access files like:
- ffplay ipfs://<cid>
- ffplay ipns://<cid>

There are multiple ways to access files on the IPFS network. This patch series
uses the gateway driven way. An IPFS node - by default - exposes a local 
gateway (say http://localhost:8080) which is then used to get content from IPFS.
The gateway functionality on the IPFS side contains optimizations to
be as ideal to streaming data as it can be. Optimizations that the http protocol
in ffmpeg also has and are thus reused for free in this approach.

A note on other "more appropiate" ways, as I received some feedback on that.
For ffmpeg purposes the gateway approach is ideal! There is a "libipfs" but
that would spin up an ipfs node with the overhead of:
- bootstrapping
- connecting to nodes
- finding other nodes to connect too
- finally finding your file

This alternative approach could take minutes before a file is played. The
gateway approach immediately connects to an already running node thus gives
the file the fastest.

Much of the logic in this patch series is to find that gateway and essentially 
rewrite:

"ipfs://<cid>"

to:

"http://localhost:8080/ipfs/<cid>"

Once that's found it's forwared to the protocol handler where eventually the
http protocol is going to handle it. Note that it could also be https. There's 
enough flexibility in the implementation to allow the user to provide a 
gateway. There are also public https gateways which can be used just as well.

After this patch is accepted, I'll work on getting IPFS supported in:
- mpv (requires this ffmpeg patch)
- vlc (prefers this patch but can be made to work without this patch)
- kodi (requires this ffmpeg patch)

Best regards,
Mark Gaiser

[1] https://docs.ipfs.io/concepts/

Mark Gaiser (1):
  avformat: Add IPFS protocol support.

 configure                 |   2 +
 doc/protocols.texi        |  30 ++++
 libavformat/Makefile      |   2 +
 libavformat/ipfsgateway.c | 329 ++++++++++++++++++++++++++++++++++++++
 libavformat/protocols.c   |   2 +
 5 files changed, 365 insertions(+)
 create mode 100644 libavformat/ipfsgateway.c

-- 
2.35.1

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[FFmpeg-devel] [PATCH v3 1/1] avformat: Add IPFS protocol support.

[Mark Gaiser]

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>
---
 configure                 |   2 +
 doc/protocols.texi        |  30 ++++
 libavformat/Makefile      |   2 +
 libavformat/ipfsgateway.c | 329 ++++++++++++++++++++++++++++++++++++++
 libavformat/protocols.c   |   2 +
 5 files changed, 365 insertions(+)
 create mode 100644 libavformat/ipfsgateway.c

diff --git a/configure b/configure
index 5b19a35f59..6ff09e7974 100755
--- a/configure
+++ b/configure
@@ -3585,6 +3585,8 @@ 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"
diff --git a/doc/protocols.texi b/doc/protocols.texi
index d207df0b52..7c9c0a4808 100644
--- a/doc/protocols.texi
+++ b/doc/protocols.texi
@@ -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 machine 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
diff --git a/libavformat/Makefile b/libavformat/Makefile
index 3dc6a479cc..4edce8420f 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -656,6 +656,8 @@ 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
diff --git a/libavformat/ipfsgateway.c b/libavformat/ipfsgateway.c
new file mode 100644
index 0000000000..72d431eac3
--- /dev/null
+++ b/libavformat/ipfsgateway.c
@@ -0,0 +1,329 @@
+/*
+ * 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 "avformat.h"
+#include "libavutil/avassert.h"
+#include "libavutil/avstring.h"
+#include "libavutil/internal.h"
+#include "libavutil/opt.h"
+#include "libavutil/tree.h"
+#include <fcntl.h>
+#if HAVE_IO_H
+#include <io.h>
+#endif
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#include "os_support.h"
+#include "url.h"
+#include <stdlib.h>
+#include <sys/stat.h>
+
+typedef struct IPFSGatewayContext {
+    AVClass *class;
+    URLContext *inner;
+    char *gateway;
+} 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.
+//
+// Return codes can be:
+// 1 : A potential gateway is found and set in c->gateway
+// -1: The IPFS data folder could not be found
+// -2: The gateway file could not be found
+// -3: The gateway file is found but empty
+// -4: $HOME is empty
+// -9: Unhandled error
+static int populate_ipfs_gateway(URLContext *h)
+{
+    IPFSGatewayContext *c = h->priv_data;
+    char *ipfs_full_data_folder = NULL;
+    char *ipfs_gateway_file = NULL;
+    struct stat st;
+    int stat_ret = 0;
+    int ret = -9;
+    FILE *gateway_file = NULL;
+    char gateway_file_data[1000];
+
+    // First, test if there already is a path in c->gateway. If it is then it
+    // was provided as cli arument and should be used. It takes precdence.
+    if (c->gateway != NULL) {
+        ret = 1;
+        goto err;
+    }
+
+    // Test $IPFS_GATEWAY.
+    if (getenv("IPFS_GATEWAY") != NULL) {
+        av_free(c->gateway);
+        c->gateway = av_asprintf("%s", getenv("IPFS_GATEWAY"));
+        ret = 1;
+        goto err;
+    } else
+        av_log(h, AV_LOG_DEBUG, "$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, "$IPFS_PATH is empty.\n");
+
+        // Try via the home folder.
+        if (getenv("HOME") == NULL) {
+            av_log(h, AV_LOG_ERROR, "$HOME appears to be empty.\n");
+            ret = -4;
+            goto err;
+        }
+
+        ipfs_full_data_folder = av_asprintf("%s/.ipfs/", getenv("HOME"));
+
+        // Stat the folder.
+        // It should exist in a default IPFS setup when run as local user.
+#ifndef _WIN32
+        stat_ret = stat(ipfs_full_data_folder, &st);
+#else
+        stat_ret = win32_stat(ipfs_full_data_folder, &st);
+#endif
+        if (stat_ret < 0) {
+            av_log(h, AV_LOG_DEBUG, "Unable to find IPFS folder. We tried:\n");
+            av_log(h, AV_LOG_DEBUG, "- $IPFS_PATH, which was empty.\n");
+            av_log(h, AV_LOG_DEBUG, "- $HOME/.ipfs (full uri: %s) which doesn't exist.\n", ipfs_full_data_folder);
+            ret = -1;
+            goto err;
+        }
+    } else
+        ipfs_full_data_folder = av_asprintf("%s", getenv("IPFS_PATH"));
+
+    ipfs_gateway_file = av_asprintf("%sgateway", ipfs_full_data_folder);
+
+    // Get the contents of the gateway file.
+    gateway_file = av_fopen_utf8(ipfs_gateway_file, "r");
+    if (!gateway_file) {
+        av_log(h, AV_LOG_ERROR, "The IPFS gateway file (full uri: %s) doesn't exist. Is the gateway enabled?\n", ipfs_gateway_file);
+        ret = -2;
+        goto err;
+    }
+
+    // Read a single line (fgets stops at new line mark).
+    fgets(gateway_file_data, sizeof(gateway_file_data) - 1, gateway_file);
+
+    // Replace first occurence of end of line to \0
+    gateway_file_data[strcspn(gateway_file_data, "\r\n")] = 0;
+
+    // If strlen finds anything longer then 0 characters then we have a
+    // potential gateway url.
+    if (strlen(gateway_file_data) < 1) {
+        av_log(h, AV_LOG_ERROR, "The IPFS gateway file (full uri: %s) appears to be empty. Is the gateway started?\n", ipfs_gateway_file);
+        ret = -3;
+        goto err;
+    }
+
+    // At this point gateway_file_data contains at least something.
+    // Copy it into c->gateway.
+    c->gateway = av_asprintf("%s", gateway_file_data);
+    if (c->gateway) {
+        ret = 1;
+        goto err;
+    } else
+        av_log(h, AV_LOG_DEBUG, "Unknown error in the IPFS gateway file.\n");
+
+err:
+    if (gateway_file)
+        fclose(gateway_file);
+
+    av_free(ipfs_full_data_folder);
+    av_free(ipfs_gateway_file);
+    return ret;
+}
+
+// For now just makes sure that the gateway ends in url we expect.
+// Like http://localhost:8080/.
+// Explicitly with the traling slash.
+//
+// Return codes can be: (any code above 0 is OK)
+// 2 : c->gateway modified to add a trailing "/"
+// 1 : c->gateway is set with a string that looks to be a valid URL
+// -1: The gateway is too short to be any kind of URL.
+// -2: The gateway didn't start with http:// or https://
+// -3: The gateway url part (without the protocol) is too short. We expect 3
+//     characters minimal. So http://aaa would be the bare minimal.
+// -9: Unhandled error
+static int sanitize_ipfs_gateway(URLContext *h)
+{
+    IPFSGatewayContext *c = h->priv_data;
+    char last_gateway_char;
+    const char *url_without_protocol;
+    const char *uri = c->gateway;
+    int ret = -9;
+
+    // "http://" is already 7 characters. Lets be really conservative and say a
+    // url must be 10 chatacters at the very least.
+    if (strlen(c->gateway) < 10) {
+        av_log(h, AV_LOG_ERROR, "The gateway URL must be at least 10 characters long.\n");
+        ret = -1;
+        goto err;
+    }
+
+    // Test if the gateway starts with either http:// or https://
+    // The remainder is stored in url_without_protocol
+    if (av_stristart(uri, "http://", &url_without_protocol) == 0
+        && av_stristart(uri, "https://", &url_without_protocol) == 0) {
+        av_log(h, AV_LOG_ERROR, "The gateway URL didn't start with http:// or https:// and is therefore invalid.\n");
+        ret = -2;
+        goto err;
+    }
+
+    // We now know the remainder of the url without the protocol. Check it for
+    // some length. At least 3 characters.
+    if (strlen(url_without_protocol) < 3) {
+        av_log(h, AV_LOG_ERROR, "The gateway url (without the protocol part) is too short to be a valid URL.\n");
+        ret = -3;
+        goto err;
+    }
+
+    last_gateway_char = c->gateway[strlen(c->gateway) - 1];
+
+    if (last_gateway_char != '/') {
+        c->gateway = av_asprintf("%s/", c->gateway);
+        ret = 2;
+        goto err;
+    }
+
+err:
+    return ret;
+}
+
+static int translate_ipfs_to_http(URLContext *h, const char *uri,
+                                  int flags, AVDictionary **options)
+{
+    const char *ipfs_cid;
+    const char *protocol_path_suffix = "ipfs/";
+    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)
+                   || av_stristart(uri, "ipfs:", &ipfs_cid));
+    int is_ipns = (av_stristart(uri, "ipns://", &ipfs_cid)
+                   || av_stristart(uri, "ipns:", &ipfs_cid));
+
+    // Populate the IPFS gateway if we have any.
+    // If not, inform the user how to properly set one.
+    if (populate_ipfs_gateway(h) < 0) {
+        av_log(h, AV_LOG_ERROR, "No IPFS gateway was set. Make sure a local IPFS instance is running.\n");
+        av_log(h, AV_LOG_INFO, "There are multiple options to define this gateway. The below options are in order of precedence:\n");
+        av_log(h, AV_LOG_INFO, "1. Define a -gateway <url> to the gateway without trailing forward slash.\n");
+        av_log(h, AV_LOG_INFO, "2. Define $IPFS_GATEWAY with the full http link to the gateway without trailing forward slash.\n");
+        av_log(h, AV_LOG_INFO, "3. Define $IPFS_PATH and point it to the IPFS data path.\n");
+        av_log(h, AV_LOG_INFO, "4. Have IPFS running in your local user folder (under $HOME/.ipfs).\n");
+        av_log(h, AV_LOG_INFO, "In all path cases, a file named gateway is expected. See https://github.com/ipfs/specs/issues/261 for more information.\n");
+        ret = AVERROR(EINVAL);
+        goto err;
+    }
+
+    // Sanitize the gateway to a format we expect.
+    if (sanitize_ipfs_gateway(h) < 1)
+        goto err;
+
+    // We must have either ipns or ipfs.
+    if (!is_ipfs && !is_ipns) {
+        ret = AVERROR(EINVAL);
+        av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
+        goto err;
+    }
+
+    // If we have IPNS, update the protocol.
+    if (is_ipns)
+        protocol_path_suffix = "ipns/";
+
+    // Concatenate the url.
+    // This ends up with something like: http://localhost:8080/ipfs/Qm.....
+    fulluri = av_asprintf("%s%s%s", c->gateway, protocol_path_suffix, ipfs_cid);
+
+    // Pass the URL back to FFMpeg's protocol handler.
+    if ((ret = ffurl_open_whitelist(&c->inner, fulluri, flags,
+                                    &h->interrupt_callback, options,
+                                    h->protocol_whitelist,
+                                    h->protocol_blacklist, h))
+        < 0) {
+        av_log(h, AV_LOG_ERROR, "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,
+};
diff --git a/libavformat/protocols.c b/libavformat/protocols.c
index 948fae411f..675b684bd3 100644
--- a/libavformat/protocols.c
+++ b/libavformat/protocols.c
@@ -73,6 +73,8 @@ 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"
 
-- 
2.35.1

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Re: [FFmpeg-devel] [PATCH v2 0/1] Add IPFS protocol support.

[Mark Gaiser]

Ignore this one, the title went wrong.

On Thu, Feb 3, 2022 at 6:26 PM Mark Gaiser <markg85@gmail.com> wrote:

> Hi,
>
> This patch series adds support for IPFS.
> V3:
> - A lot of style changes
> - Made url checks a lot more strict
> - av_asprintf leak fixes
> - So many changes that a diff to v2 is again not sensible.
> V2:
> - Squashed and changed so much that a diff to v1 was not sensible.
>
> The following is a short summary. In the IPFS ecosystem you access it's
> content
> by a "Content IDentifier" (CID). This CID is, in simplified terms, a hash
> of
> the content. IPFS itself is a distributed network where any user can run a
> node
> to be part of the network and access files by their CID. If any reachable
> node
> within that network has the CID, you can get it.
>
> IPFS (as a technology) has two protocols, ipfs and ipns.
> The ipfs protocol is the immutable way to access content.
> The ipns protocol is a mutable layer on top of it. It's essentially a new
> CID
> that points to a ipfs CID. This "pointer" if you will can be changed to
> point
> to something else.
> Much more information on how this technology works can be found here [1].
>
> This patch series allows to interact natively with IPFS. That means being
> able
> to access files like:
> - ffplay ipfs://<cid>
> - ffplay ipns://<cid>
>
> There are multiple ways to access files on the IPFS network. This patch
> series
> uses the gateway driven way. An IPFS node - by default - exposes a local
> gateway (say http://localhost:8080) which is then used to get content
> from IPFS.
> The gateway functionality on the IPFS side contains optimizations to
> be as ideal to streaming data as it can be. Optimizations that the http
> protocol
> in ffmpeg also has and are thus reused for free in this approach.
>
> A note on other "more appropiate" ways, as I received some feedback on
> that.
> For ffmpeg purposes the gateway approach is ideal! There is a "libipfs" but
> that would spin up an ipfs node with the overhead of:
> - bootstrapping
> - connecting to nodes
> - finding other nodes to connect too
> - finally finding your file
>
> This alternative approach could take minutes before a file is played. The
> gateway approach immediately connects to an already running node thus gives
> the file the fastest.
>
> Much of the logic in this patch series is to find that gateway and
> essentially
> rewrite:
>
> "ipfs://<cid>"
>
> to:
>
> "http://localhost:8080/ipfs/<cid>"
>
> Once that's found it's forwared to the protocol handler where eventually
> the
> http protocol is going to handle it. Note that it could also be https.
> There's
> enough flexibility in the implementation to allow the user to provide a
> gateway. There are also public https gateways which can be used just as
> well.
>
> After this patch is accepted, I'll work on getting IPFS supported in:
> - mpv (requires this ffmpeg patch)
> - vlc (prefers this patch but can be made to work without this patch)
> - kodi (requires this ffmpeg patch)
>
> Best regards,
> Mark Gaiser
>
> [1] https://docs.ipfs.io/concepts/
>
> Mark Gaiser (1):
>   avformat: Add IPFS protocol support.
>
>  configure                 |   2 +
>  doc/protocols.texi        |  30 ++++
>  libavformat/Makefile      |   2 +
>  libavformat/ipfsgateway.c | 329 ++++++++++++++++++++++++++++++++++++++
>  libavformat/protocols.c   |   2 +
>  5 files changed, 365 insertions(+)
>  create mode 100644 libavformat/ipfsgateway.c
>
> --
> 2.35.1
>
>
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Re: [FFmpeg-devel] [PATCH v3 1/1] avformat: Add IPFS protocol support.

[Mark Gaiser]

Ignore this one, the title went wrong.

On Thu, Feb 3, 2022 at 6:26 PM Mark Gaiser <markg85@gmail.com> wrote:

> 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>
> ---
>  configure                 |   2 +
>  doc/protocols.texi        |  30 ++++
>  libavformat/Makefile      |   2 +
>  libavformat/ipfsgateway.c | 329 ++++++++++++++++++++++++++++++++++++++
>  libavformat/protocols.c   |   2 +
>  5 files changed, 365 insertions(+)
>  create mode 100644 libavformat/ipfsgateway.c
>
> diff --git a/configure b/configure
> index 5b19a35f59..6ff09e7974 100755
> --- a/configure
> +++ b/configure
> @@ -3585,6 +3585,8 @@ 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"
> diff --git a/doc/protocols.texi b/doc/protocols.texi
> index d207df0b52..7c9c0a4808 100644
> --- a/doc/protocols.texi
> +++ b/doc/protocols.texi
> @@ -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 machine 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
> diff --git a/libavformat/Makefile b/libavformat/Makefile
> index 3dc6a479cc..4edce8420f 100644
> --- a/libavformat/Makefile
> +++ b/libavformat/Makefile
> @@ -656,6 +656,8 @@ 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
> diff --git a/libavformat/ipfsgateway.c b/libavformat/ipfsgateway.c
> new file mode 100644
> index 0000000000..72d431eac3
> --- /dev/null
> +++ b/libavformat/ipfsgateway.c
> @@ -0,0 +1,329 @@
> +/*
> + * 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 "avformat.h"
> +#include "libavutil/avassert.h"
> +#include "libavutil/avstring.h"
> +#include "libavutil/internal.h"
> +#include "libavutil/opt.h"
> +#include "libavutil/tree.h"
> +#include <fcntl.h>
> +#if HAVE_IO_H
> +#include <io.h>
> +#endif
> +#if HAVE_UNISTD_H
> +#include <unistd.h>
> +#endif
> +#include "os_support.h"
> +#include "url.h"
> +#include <stdlib.h>
> +#include <sys/stat.h>
> +
> +typedef struct IPFSGatewayContext {
> +    AVClass *class;
> +    URLContext *inner;
> +    char *gateway;
> +} 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.
> +//
> +// Return codes can be:
> +// 1 : A potential gateway is found and set in c->gateway
> +// -1: The IPFS data folder could not be found
> +// -2: The gateway file could not be found
> +// -3: The gateway file is found but empty
> +// -4: $HOME is empty
> +// -9: Unhandled error
> +static int populate_ipfs_gateway(URLContext *h)
> +{
> +    IPFSGatewayContext *c = h->priv_data;
> +    char *ipfs_full_data_folder = NULL;
> +    char *ipfs_gateway_file = NULL;
> +    struct stat st;
> +    int stat_ret = 0;
> +    int ret = -9;
> +    FILE *gateway_file = NULL;
> +    char gateway_file_data[1000];
> +
> +    // First, test if there already is a path in c->gateway. If it is
> then it
> +    // was provided as cli arument and should be used. It takes precdence.
> +    if (c->gateway != NULL) {
> +        ret = 1;
> +        goto err;
> +    }
> +
> +    // Test $IPFS_GATEWAY.
> +    if (getenv("IPFS_GATEWAY") != NULL) {
> +        av_free(c->gateway);
> +        c->gateway = av_asprintf("%s", getenv("IPFS_GATEWAY"));
> +        ret = 1;
> +        goto err;
> +    } else
> +        av_log(h, AV_LOG_DEBUG, "$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, "$IPFS_PATH is empty.\n");
> +
> +        // Try via the home folder.
> +        if (getenv("HOME") == NULL) {
> +            av_log(h, AV_LOG_ERROR, "$HOME appears to be empty.\n");
> +            ret = -4;
> +            goto err;
> +        }
> +
> +        ipfs_full_data_folder = av_asprintf("%s/.ipfs/", getenv("HOME"));
> +
> +        // Stat the folder.
> +        // It should exist in a default IPFS setup when run as local user.
> +#ifndef _WIN32
> +        stat_ret = stat(ipfs_full_data_folder, &st);
> +#else
> +        stat_ret = win32_stat(ipfs_full_data_folder, &st);
> +#endif
> +        if (stat_ret < 0) {
> +            av_log(h, AV_LOG_DEBUG, "Unable to find IPFS folder. We
> tried:\n");
> +            av_log(h, AV_LOG_DEBUG, "- $IPFS_PATH, which was empty.\n");
> +            av_log(h, AV_LOG_DEBUG, "- $HOME/.ipfs (full uri: %s) which
> doesn't exist.\n", ipfs_full_data_folder);
> +            ret = -1;
> +            goto err;
> +        }
> +    } else
> +        ipfs_full_data_folder = av_asprintf("%s", getenv("IPFS_PATH"));
> +
> +    ipfs_gateway_file = av_asprintf("%sgateway", ipfs_full_data_folder);
> +
> +    // Get the contents of the gateway file.
> +    gateway_file = av_fopen_utf8(ipfs_gateway_file, "r");
> +    if (!gateway_file) {
> +        av_log(h, AV_LOG_ERROR, "The IPFS gateway file (full uri: %s)
> doesn't exist. Is the gateway enabled?\n", ipfs_gateway_file);
> +        ret = -2;
> +        goto err;
> +    }
> +
> +    // Read a single line (fgets stops at new line mark).
> +    fgets(gateway_file_data, sizeof(gateway_file_data) - 1, gateway_file);
> +
> +    // Replace first occurence of end of line to \0
> +    gateway_file_data[strcspn(gateway_file_data, "\r\n")] = 0;
> +
> +    // If strlen finds anything longer then 0 characters then we have a
> +    // potential gateway url.
> +    if (strlen(gateway_file_data) < 1) {
> +        av_log(h, AV_LOG_ERROR, "The IPFS gateway file (full uri: %s)
> appears to be empty. Is the gateway started?\n", ipfs_gateway_file);
> +        ret = -3;
> +        goto err;
> +    }
> +
> +    // At this point gateway_file_data contains at least something.
> +    // Copy it into c->gateway.
> +    c->gateway = av_asprintf("%s", gateway_file_data);
> +    if (c->gateway) {
> +        ret = 1;
> +        goto err;
> +    } else
> +        av_log(h, AV_LOG_DEBUG, "Unknown error in the IPFS gateway
> file.\n");
> +
> +err:
> +    if (gateway_file)
> +        fclose(gateway_file);
> +
> +    av_free(ipfs_full_data_folder);
> +    av_free(ipfs_gateway_file);
> +    return ret;
> +}
> +
> +// For now just makes sure that the gateway ends in url we expect.
> +// Like http://localhost:8080/.
> +// Explicitly with the traling slash.
> +//
> +// Return codes can be: (any code above 0 is OK)
> +// 2 : c->gateway modified to add a trailing "/"
> +// 1 : c->gateway is set with a string that looks to be a valid URL
> +// -1: The gateway is too short to be any kind of URL.
> +// -2: The gateway didn't start with http:// or https://
> +// -3: The gateway url part (without the protocol) is too short. We
> expect 3
> +//     characters minimal. So http://aaa would be the bare minimal.
> +// -9: Unhandled error
> +static int sanitize_ipfs_gateway(URLContext *h)
> +{
> +    IPFSGatewayContext *c = h->priv_data;
> +    char last_gateway_char;
> +    const char *url_without_protocol;
> +    const char *uri = c->gateway;
> +    int ret = -9;
> +
> +    // "http://" is already 7 characters. Lets be really conservative
> and say a
> +    // url must be 10 chatacters at the very least.
> +    if (strlen(c->gateway) < 10) {
> +        av_log(h, AV_LOG_ERROR, "The gateway URL must be at least 10
> characters long.\n");
> +        ret = -1;
> +        goto err;
> +    }
> +
> +    // Test if the gateway starts with either http:// or https://
> +    // The remainder is stored in url_without_protocol
> +    if (av_stristart(uri, "http://", &url_without_protocol) == 0
> +        && av_stristart(uri, "https://", &url_without_protocol) == 0) {
> +        av_log(h, AV_LOG_ERROR, "The gateway URL didn't start with http://
> or https:// and is therefore invalid.\n");
> +        ret = -2;
> +        goto err;
> +    }
> +
> +    // We now know the remainder of the url without the protocol. Check
> it for
> +    // some length. At least 3 characters.
> +    if (strlen(url_without_protocol) < 3) {
> +        av_log(h, AV_LOG_ERROR, "The gateway url (without the protocol
> part) is too short to be a valid URL.\n");
> +        ret = -3;
> +        goto err;
> +    }
> +
> +    last_gateway_char = c->gateway[strlen(c->gateway) - 1];
> +
> +    if (last_gateway_char != '/') {
> +        c->gateway = av_asprintf("%s/", c->gateway);
> +        ret = 2;
> +        goto err;
> +    }
> +
> +err:
> +    return ret;
> +}
> +
> +static int translate_ipfs_to_http(URLContext *h, const char *uri,
> +                                  int flags, AVDictionary **options)
> +{
> +    const char *ipfs_cid;
> +    const char *protocol_path_suffix = "ipfs/";
> +    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)
> +                   || av_stristart(uri, "ipfs:", &ipfs_cid));
> +    int is_ipns = (av_stristart(uri, "ipns://", &ipfs_cid)
> +                   || av_stristart(uri, "ipns:", &ipfs_cid));
> +
> +    // Populate the IPFS gateway if we have any.
> +    // If not, inform the user how to properly set one.
> +    if (populate_ipfs_gateway(h) < 0) {
> +        av_log(h, AV_LOG_ERROR, "No IPFS gateway was set. Make sure a
> local IPFS instance is running.\n");
> +        av_log(h, AV_LOG_INFO, "There are multiple options to define this
> gateway. The below options are in order of precedence:\n");
> +        av_log(h, AV_LOG_INFO, "1. Define a -gateway <url> to the gateway
> without trailing forward slash.\n");
> +        av_log(h, AV_LOG_INFO, "2. Define $IPFS_GATEWAY with the full
> http link to the gateway without trailing forward slash.\n");
> +        av_log(h, AV_LOG_INFO, "3. Define $IPFS_PATH and point it to the
> IPFS data path.\n");
> +        av_log(h, AV_LOG_INFO, "4. Have IPFS running in your local user
> folder (under $HOME/.ipfs).\n");
> +        av_log(h, AV_LOG_INFO, "In all path cases, a file named gateway
> is expected. See https://github.com/ipfs/specs/issues/261 for more
> information.\n");
> +        ret = AVERROR(EINVAL);
> +        goto err;
> +    }
> +
> +    // Sanitize the gateway to a format we expect.
> +    if (sanitize_ipfs_gateway(h) < 1)
> +        goto err;
> +
> +    // We must have either ipns or ipfs.
> +    if (!is_ipfs && !is_ipns) {
> +        ret = AVERROR(EINVAL);
> +        av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
> +        goto err;
> +    }
> +
> +    // If we have IPNS, update the protocol.
> +    if (is_ipns)
> +        protocol_path_suffix = "ipns/";
> +
> +    // Concatenate the url.
> +    // This ends up with something like: http://localhost:8080/ipfs/Qm...
> ..
> +    fulluri = av_asprintf("%s%s%s", c->gateway, protocol_path_suffix,
> ipfs_cid);
> +
> +    // Pass the URL back to FFMpeg's protocol handler.
> +    if ((ret = ffurl_open_whitelist(&c->inner, fulluri, flags,
> +                                    &h->interrupt_callback, options,
> +                                    h->protocol_whitelist,
> +                                    h->protocol_blacklist, h))
> +        < 0) {
> +        av_log(h, AV_LOG_ERROR, "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,
> +};
> diff --git a/libavformat/protocols.c b/libavformat/protocols.c
> index 948fae411f..675b684bd3 100644
> --- a/libavformat/protocols.c
> +++ b/libavformat/protocols.c
> @@ -73,6 +73,8 @@ 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"
>
> --
> 2.35.1
>
>
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