Re: [FFmpeg-devel] [PATCH 1/5] Early version of IPFS protocol support.

[James Almer <jamrial@gmail.com>]

On 1/31/2022 10:51 AM, Mark Gaiser wrote:
> Signed-off-by: Mark Gaiser <markg85@gmail.com>
> ---
>   configure               |   1 +
>   doc/protocols.texi      |  30 ++++++
>   libavformat/Makefile    |   1 +
>   libavformat/ipfs.c      | 202 ++++++++++++++++++++++++++++++++++++++++
>   libavformat/protocols.c |   2 +
>   5 files changed, 236 insertions(+)
>   create mode 100644 libavformat/ipfs.c
> 
> diff --git a/configure b/configure
> index 5b19a35f59..e466f924a3 100755
> --- a/configure
> +++ b/configure
> @@ -3585,6 +3585,7 @@ udp_protocol_select="network"
>   udplite_protocol_select="network"
>   unix_protocol_deps="sys_un_h"
>   unix_protocol_select="network"
> +ipfs_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..983a77f4f2 100644
> --- a/libavformat/Makefile
> +++ b/libavformat/Makefile
> @@ -656,6 +656,7 @@ 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-$(CONFIG_IPFS_PROTOCOL)             += ipfs.o
>   TLS-OBJS-$(CONFIG_GNUTLS)                += tls_gnutls.o
>   TLS-OBJS-$(CONFIG_LIBTLS)                += tls_libtls.o
>   TLS-OBJS-$(CONFIG_MBEDTLS)               += tls_mbedtls.o
> diff --git a/libavformat/ipfs.c b/libavformat/ipfs.c
> new file mode 100644
> index 0000000000..4cc65750ed
> --- /dev/null
> +++ b/libavformat/ipfs.c
> @@ -0,0 +1,202 @@
> +/*
> + * IPFS protocol.
> + * Copyright (c) 2021 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/avassert.h"
> +#include "libavutil/avstring.h"
> +#include "libavutil/internal.h"
> +#include "libavutil/opt.h"
> +#include "libavutil/tree.h"
> +#include "avformat.h"
> +#include <fcntl.h>
> +#if HAVE_IO_H
> +#include <io.h>
> +#endif
> +#if HAVE_UNISTD_H
> +#include <unistd.h>
> +#endif
> +#include <sys/stat.h>
> +#include <stdlib.h>
> +#include "os_support.h"
> +#include "url.h"
> +
> +typedef struct Context {
> +    AVClass *class;
> +    URLContext *inner;
> +    char *fulluri;
> +    char *gateway;
> +} Context;

A more descriptive name would be nice.

> +
> +static int ipfs_open(URLContext *h, const char *uri, int flags, AVDictionary **options)
> +{
> +    const char *gatewaysuffix;
> +    int ret = 0;
> +    Context *c = h->priv_data;
> +
> +    if (!av_strstart(uri, "ipfs://", &gatewaysuffix) &&
> +        !av_strstart(uri, "ipfs:", &gatewaysuffix)) {
> +        av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
> +        ret = AVERROR(EINVAL);
> +        goto err;

Just return ret. No need for this goto.

> +    }
> +
> +    char* ipfs_gateway = "https://ipfs.io/ipfs/";

const char*

> +
> +    c->fulluri = malloc(strlen(ipfs_gateway)+strlen(gatewaysuffix) + 1);

av_malloc()

Also, check the return value for allocation failure.

> +
> +    strcpy(c->fulluri, ipfs_gateway);
> +    strcat(c->fulluri, gatewaysuffix);
> +
> +    if ((ret = ffurl_open_whitelist(&c->inner, c->fulluri, flags,

Is fulluri going to be used after this call? If not, then it should be 
local to this function as there's no need to have it in h->priv_data 
(And for that matter, you're not freeing fulluri anywhere).

> +                                    &h->interrupt_callback, options,
> +                                    h->protocol_whitelist, h->protocol_blacklist, h)) < 0) {

You need to define a whitelist including https in both URLProtocol below.

> +        av_log(h, AV_LOG_ERROR, "Unable to open resource: %s\n", c->fulluri);
> +        goto err;
> +    }
> +
> +err:
> +    return ret;
> +}
> +
> +static int ipfs_read(URLContext *h, unsigned char *buf, int size)
> +{
> +    Context *c = h->priv_data;
> +    int ret;
> +
> +    ret = ffurl_read(c->inner, buf, size);
> +
> +    return ret;
> +}
> +
> +static int64_t ipfs_seek(URLContext *h, int64_t pos, int whence)
> +{
> +    Context *c = h->priv_data;
> +    int64_t ret;
> +
> +    ret = ffurl_seek(c->inner, pos, whence);
> +
> +    return ret;
> +}
> +
> +static int ipfs_close(URLContext *h)
> +{
> +    Context *c = h->priv_data;
> +    int ret;
> +
> +    ret = ffurl_closep(&c->inner);
> +
> +    return ret;
> +}
> +
> +static int ipns_open(URLContext *h, const char *uri, int flags, AVDictionary **options)
> +{
> +    const char *gatewaysuffix;
> +    int ret = 0;
> +    Context *c = h->priv_data;
> +
> +    if (!av_strstart(uri, "ipns://", &gatewaysuffix) &&
> +        !av_strstart(uri, "ipns:", &gatewaysuffix)) {
> +        av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
> +        ret = AVERROR(EINVAL);
> +        goto err;
> +    }
> +
> +    char* ipfs_gateway = "https://ipfs.io/ipns/";
> +
> +    c->fulluri = malloc(strlen(ipfs_gateway)+strlen(gatewaysuffix) + 1);
> +
> +    strcpy(c->fulluri, ipfs_gateway);
> +    strcat(c->fulluri, gatewaysuffix);
> +
> +    if ((ret = ffurl_open_whitelist(&c->inner, c->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", c->fulluri);
> +        goto err;
> +    }
> +
> +err:
> +    return ret;

Same comments as above apply here.

> +}
> +
> +static int ipns_read(URLContext *h, unsigned char *buf, int size)
> +{
> +    Context *c = h->priv_data;
> +    int ret;
> +
> +    ret = ffurl_read(c->inner, buf, size);
> +
> +    return ret;
> +}
> +
> +static int64_t ipns_seek(URLContext *h, int64_t pos, int whence)
> +{
> +    Context *c = h->priv_data;
> +    int64_t ret;
> +
> +    ret = ffurl_seek(c->inner, pos, whence);
> +
> +    return ret;
> +}
> +
> +static int ipns_close(URLContext *h)
> +{
> +    Context *c = h->priv_data;
> +    int ret;
> +
> +    ret = ffurl_closep(&c->inner);
> +
> +    return ret;
> +}
> +
> +#define OFFSET(x) offsetof(Context, x)
> +#define D AV_OPT_FLAG_DECODING_PARAM
> +
> +static const AVOption options[] = {
> +    {"gateway", "The gateway to ask for IPFS data.", OFFSET(gateway), AV_OPT_TYPE_BINARY, .flags = D },
> +    {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           = ipfs_open,
> +    .url_read            = ipfs_read,
> +    .url_seek            = ipfs_seek,
> +    .url_close           = ipfs_close,
> +    .priv_data_size      = sizeof(Context),
> +    .priv_data_class     = &ipfs_context_class,
> +};
> +
> +const URLProtocol ff_infs_protocol = {
> +    .name                = "ipns",
> +    .url_open2           = ipfs_open,
> +    .url_read            = ipfs_read,
> +    .url_seek            = ipfs_seek,
> +    .url_close           = ipfs_close,
> +    .priv_data_size      = sizeof(Context),
> +    .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"
>   
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