[PATCH] net: lwip: scale buffer pool size with TFTP block size

[Jerome Forissier]

Hi Pranav,

On 05/03/2026 07:40, Pranav Tilak wrote:
> TFTP transfers fail when tftpblocksize is set to 8192 or larger due to
> insufficient buffer resources for IP fragment reassembly.
> 
> Adjust PBUF_POOL_SIZE and IP_REASS_MAX_PBUFS based on
> CONFIG_TFTP_BLOCKSIZE to support larger TFTP transfers
> while keeping memory usage efficient.
> 
> - CONFIG_TFTP_BLOCKSIZE >= 12288:PBUF_POOL_SIZE=18, IP_REASS_MAX_PBUFS=12
> 
> - CONFIG_TFTP_BLOCKSIZE >= 8192:PBUF_POOL_SIZE=12, IP_REASS_MAX_PBUFS=6
> 
> - CONFIG_TFTP_BLOCKSIZE undefined: PBUF_POOL_SIZE=8, IP_REASS_MAX_PBUFS=4

How are these values computed? Could you find a formula instead of using
#if/#elif/#else/endif?

Thanks,
-- 
Jerome

> Signed-off-by: Pranav Tilak <pranav.vinaytilak at amd.com>
> ---
>  lib/lwip/u-boot/lwipopts.h | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/lib/lwip/u-boot/lwipopts.h b/lib/lwip/u-boot/lwipopts.h
> index e8a2c9d7a0a..b4ff31096fe 100644
> --- a/lib/lwip/u-boot/lwipopts.h
> +++ b/lib/lwip/u-boot/lwipopts.h
> @@ -65,7 +65,14 @@
>  #define MEM_ALIGNMENT                   8
>  
>  #define MEMP_NUM_TCP_SEG                16
> +
> +#if defined(CONFIG_TFTP_BLOCKSIZE) && CONFIG_TFTP_BLOCKSIZE >= 12288
> +#define PBUF_POOL_SIZE                  18
> +#elif defined(CONFIG_TFTP_BLOCKSIZE) && CONFIG_TFTP_BLOCKSIZE >= 8192
> +#define PBUF_POOL_SIZE                  12
> +#else
>  #define PBUF_POOL_SIZE                  8
> +#endif
>  
>  #define LWIP_ARP                        1
>  #define ARP_TABLE_SIZE                  4
> @@ -76,7 +83,15 @@
>  #define IP_REASSEMBLY                   1
>  #define IP_FRAG                         1
>  #define IP_REASS_MAXAGE                 3
> +
> +#if defined(CONFIG_TFTP_BLOCKSIZE) && CONFIG_TFTP_BLOCKSIZE >= 12288
> +#define IP_REASS_MAX_PBUFS              12
> +#elif defined(CONFIG_TFTP_BLOCKSIZE) && CONFIG_TFTP_BLOCKSIZE >= 8192
> +#define IP_REASS_MAX_PBUFS              6
> +#else
>  #define IP_REASS_MAX_PBUFS              4
> +#endif
> +
>  #define IP_FRAG_USES_STATIC_BUF         0
>  
>  #define IP_DEFAULT_TTL                  255