Re: [FFmpeg-devel] [PATCH v2 2/8] avformat/udp: make recv addr of each packet available

[Jack Lau <jacklau1222gm-at-gmail.com@ffmpeg.org>]

> On Jul 7, 2025, at 02:36, Timo Rothenpieler <timo@rothenpieler.org> wrote:
> 
> ---
> libavformat/network.h |  2 ++
> libavformat/udp.c     | 25 +++++++++++++++++--------
> 2 files changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/libavformat/network.h b/libavformat/network.h
> index ca214087fc..48bb75a758 100644
> --- a/libavformat/network.h
> +++ b/libavformat/network.h
> @@ -338,4 +338,6 @@ int ff_connect_parallel(struct addrinfo *addrs, int timeout_ms_per_address,
>                         int parallel, URLContext *h, int *fd,
>                         int (*customize_fd)(void *, int, int), void *customize_ctx);
> 
> +void ff_udp_get_last_recv_addr(URLContext *h, struct sockaddr_storage *addr);
> +
> #endif /* AVFORMAT_NETWORK_H */
> diff --git a/libavformat/udp.c b/libavformat/udp.c
> index 30f075de8e..7d64ff07ed 100644
> --- a/libavformat/udp.c
> +++ b/libavformat/udp.c
> @@ -107,7 +107,7 @@ typedef struct UDPContext {
>     pthread_cond_t cond;
>     int thread_started;
> #endif
> -    uint8_t tmp[UDP_MAX_PKT_SIZE+4];
> +    uint8_t tmp[UDP_MAX_PKT_SIZE + 4 + sizeof(struct sockaddr_storage)];
>     int remaining_in_dg;
>     char *localaddr;
>     int timeout;
> @@ -115,6 +115,7 @@ typedef struct UDPContext {
>     char *sources;
>     char *block;
>     IPSourceFilters filters;
> +    struct sockaddr_storage last_recv_addr;
> } UDPContext;
> 
> #define OFFSET(x) offsetof(UDPContext, x)
> @@ -467,6 +468,12 @@ int ff_udp_get_local_port(URLContext *h)
>     return s->local_port;
> }
> 
> +void ff_udp_get_last_recv_addr(URLContext *h, struct sockaddr_storage *addr)
> +{
> +    UDPContext *s = h->priv_data;
> +    *addr = s->last_recv_addr;
> +}
> +
> /**
>  * Return the udp file handle for select() usage to wait for several RTP
>  * streams at the same time.
> @@ -498,13 +505,14 @@ static void *circular_buffer_task_rx( void *_URLContext)
>         int len;
>         struct sockaddr_storage addr;
>         socklen_t addr_len = sizeof(addr);
> +        const int header_sz = 4 + addr_len;
> 
>         pthread_mutex_unlock(&s->mutex);
>         /* Blocking operations are always cancellation points;
>            see "General Information" / "Thread Cancelation Overview"
>            in Single Unix. */
>         pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &old_cancelstate);
> -        len = recvfrom(s->udp_fd, s->tmp+4, sizeof(s->tmp)-4, 0, (struct sockaddr *)&addr, &addr_len);
> +        len = recvfrom(s->udp_fd, s->tmp + header_sz, sizeof(s->tmp) - header_sz, 0, (struct sockaddr *)&addr, &addr_len);
>         pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old_cancelstate);
>         pthread_mutex_lock(&s->mutex);
>         if (len < 0) {
> @@ -517,8 +525,9 @@ static void *circular_buffer_task_rx( void *_URLContext)
>         if (ff_ip_check_source_lists(&addr, &s->filters))
>             continue;
>         AV_WL32(s->tmp, len);
> +        memcpy(s->tmp + 4, &addr, sizeof(addr));
> 
> -        if (av_fifo_can_write(s->fifo) < len + 4) {
> +        if (av_fifo_can_write(s->fifo) < len + header_sz) {
>             /* No Space left */
>             if (s->overrun_nonfatal) {
>                 av_log(h, AV_LOG_WARNING, "Circular buffer overrun. "
> @@ -532,7 +541,7 @@ static void *circular_buffer_task_rx( void *_URLContext)
>                 goto end;
>             }
>         }
> -        av_fifo_write(s->fifo, s->tmp, len + 4);
> +        av_fifo_write(s->fifo, s->tmp, len + header_sz);
>         pthread_cond_signal(&s->cond);
>     }
> 
> @@ -991,8 +1000,7 @@ static int udp_read(URLContext *h, uint8_t *buf, int size)
> {
>     UDPContext *s = h->priv_data;
>     int ret;
> -    struct sockaddr_storage addr;
> -    socklen_t addr_len = sizeof(addr);
> +    socklen_t addr_len = sizeof(s->last_recv_addr);
> #if HAVE_PTHREAD_CANCEL
>     int avail, nonblock = h->flags & AVIO_FLAG_NONBLOCK;
> 
> @@ -1004,6 +1012,7 @@ static int udp_read(URLContext *h, uint8_t *buf, int size)
>                 uint8_t tmp[4];
> 
>                 av_fifo_read(s->fifo, tmp, 4);
> +                av_fifo_read(s->fifo, &s->last_recv_addr, sizeof(s->last_recv_addr));
>                 avail = AV_RL32(tmp);
>                 if(avail > size){
>                     av_log(h, AV_LOG_WARNING, "Part of datagram lost due to insufficient buffer size\n");
> @@ -1043,10 +1052,10 @@ static int udp_read(URLContext *h, uint8_t *buf, int size)
>         if (ret < 0)
>             return ret;
>     }
> -    ret = recvfrom(s->udp_fd, buf, size, 0, (struct sockaddr *)&addr, &addr_len);
> +    ret = recvfrom(s->udp_fd, buf, size, 0, (struct sockaddr *)&s->last_recv_addr, &addr_len);
>     if (ret < 0)
>         return ff_neterrno();
> -    if (ff_ip_check_source_lists(&addr, &s->filters))
> +    if (ff_ip_check_source_lists(&s->last_recv_addr, &s->filters))
>         return AVERROR(EINTR);
>     return ret;
> }
> -- 
> 2.49.0
> 
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I think it’s necessary to add "socklen_t last_recv_len".
I’ve send the fixes to your GitHub repo https://github.com/BtbN/FFmpeg/pull/3 because my fixes depends your patchset.

Best regards
Jack


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