Hi,
On Mon, 25 Sep 2023 13:29:34 -0700 seanedm...@linux.microsoft.com wrote:
> From: Sean Edmond <seanedm...@microsoft.com>
>
> This patch introduces 3 improvements to align with RFC 951:
> - retransmission backoff interval maximum is configurable
> - initial retranmission backoff interval is configurable
> - transaction ID is kept the same for each BOOTP/DHCPv4 request
>
> In applications where thousands of nodes are serviced by a single DHCP
> server, maximizing the retransmission backoff interval at 2 seconds (the
> current u-boot default) exerts high pressure on the DHCP server and
> network layer.
>
> RFC 951 “7.2. Client Retransmission Strategy” states that the
> retransmission backoff interval should maximize at 60 seconds. This
> patch allows the interval to be configurable using the environment
> variable "bootpretransmitperiodmax"
>
> The initial retranmission backoff period defaults to 250ms, which is
> also too small for these scenarios with many clients. This patch makes
> the initial retransmission interval to be configurable using the
> environment variable "bootpretransmitperiodinit".
>
> Also, on a retransmission it is not expected for the transaction ID to
> change (only the 'secs' field should be updated). Let's save the
> transaction ID and use the same transaction ID for each BOOTP/DHCPv4
> exchange.
>
> Signed-off-by: Sean Edmond <seanedm...@microsoft.com>
> ---
> net/bootp.c | 63 +++++++++++++++++++++++++++++++++++++++--------------
> 1 file changed, 47 insertions(+), 16 deletions(-)
>
> diff --git a/net/bootp.c b/net/bootp.c
> index 013d54c7ed..7248536cc4 100644
> --- a/net/bootp.c
> +++ b/net/bootp.c
> @@ -42,6 +42,17 @@
> */
> #define TIMEOUT_MS ((3 + (CONFIG_NET_RETRY_COUNT * 5)) * 1000)
>
> +/*
> + * According to rfc951 : 7.2. Client Retransmission Strategy
> + * "After the 'average' backoff reaches about 60 seconds, it should be
> + * increased no further, but still randomized."
> + *
> + * U-Boot has saturated this backoff at 2 seconds for a long time.
> + * To modify, set the environment variable "bootpretransmitperiodmax"
> + */
> +#define RETRANSMIT_PERIOD_MAX_MS 2000
> +#define RETRANSMIT_PERIOD_INIT_MS 250
> +
> #define PORT_BOOTPS 67 /* BOOTP server UDP port */
> #define PORT_BOOTPC 68 /* BOOTP client UDP port */
>
> @@ -56,6 +67,7 @@
> u32 bootp_ids[CFG_BOOTP_ID_CACHE_SIZE];
> unsigned int bootp_num_ids;
> int bootp_try;
> +u32 bootp_id;
> ulong bootp_start;
> ulong bootp_timeout;
> char net_nis_domain[32] = {0,}; /* Our NIS domain */
> @@ -63,6 +75,7 @@ char net_hostname[32] = {0,}; /* Our hostname */
> char net_root_path[CONFIG_BOOTP_MAX_ROOT_PATH_LEN] = {0,}; /* Our bootpath */
>
> static ulong time_taken_max;
> +static u32 retransmit_period_max_ms;
>
> #if defined(CONFIG_CMD_DHCP)
> static dhcp_state_t dhcp_state = INIT;
> @@ -417,8 +430,8 @@ static void bootp_timeout_handler(void)
> }
> } else {
> bootp_timeout *= 2;
> - if (bootp_timeout > 2000)
> - bootp_timeout = 2000;
> + if (bootp_timeout > retransmit_period_max_ms)
> + bootp_timeout = retransmit_period_max_ms;
> net_set_timeout_handler(bootp_timeout, bootp_timeout_handler);
> bootp_request();
> }
> @@ -714,10 +727,18 @@ static int bootp_extended(u8 *e)
>
> void bootp_reset(void)
> {
> + char *ep; /* Environment pointer */
> +
> bootp_num_ids = 0;
> bootp_try = 0;
> bootp_start = get_timer(0);
> - bootp_timeout = 250;
> +
> + ep = env_get("bootpretransmitperiodinit");
> + if (ep)
> + bootp_timeout = dectoul(ep, NULL);
> + else
> + bootp_timeout = RETRANSMIT_PERIOD_INIT_MS;
> +
bootp_timeout = env_get_ulong("bootpretransmitperiodinit", 0,
RETRANSMIT_PERIOD_INIT_MS);
does the same...
> }
>
> void bootp_request(void)
> @@ -729,7 +750,6 @@ void bootp_request(void)
> #ifdef CONFIG_BOOTP_RANDOM_DELAY
> ulong rand_ms;
> #endif
> - u32 bootp_id;
> struct in_addr zero_ip;
> struct in_addr bcast_ip;
> char *ep; /* Environment pointer */
> @@ -745,6 +765,12 @@ void bootp_request(void)
> else
> time_taken_max = TIMEOUT_MS;
>
> + ep = env_get("bootpretransmitperiodmax");
> + if (ep)
> + retransmit_period_max_ms = dectoul(ep, NULL);
> + else
> + retransmit_period_max_ms = RETRANSMIT_PERIOD_MAX_MS;
> +
see above
Lothar Waßmann
