[Buildroot] [PATCH 1/1] package/busybox: speed up DHCP lease acquisition

[Buildroot] [PATCH 1/1] package/busybox: speed up DHCP lease acquisition

[Edgar Bonet]

Commit c343e01ac4908f76520cf9a405ed87650e78dc62 made udhcpc send a
single DHCP request (instead of 3) before going to the background, thus
speeding up the boot process if the DHCP lease is not obtained
immediately. Unfortunately, this can also slow down the acquisition of
the lease as, after going to the background, udhcpc waits for 20 seconds
(instead of 3) before retrying.

Speed up the lease acquisition by setting the retry timeout to 3
seconds.

Signed-off-by: Edgar Bonet <bonet@grenoble.cnrs.fr>
---
Hello!

While testing 2022.08-rc1 with acmesystems_acqua_a5_512mb_defconfig on a
real Acqua board (and Ubuntu 20.04 host), I noticed that my board became
very slow in getting a DHCP lease, which was a fast process on 2022.05.
Wireshark showed the following DHCP traffic ("<" = received from the
board, ">" = sent to the board):

    time (s)  packet
    ---------------------
    03.24 < DHCP Discover
    06.24 > DHCP Offer
    26.28 < DHCP Discover
    26.28 > DHCP Offer
    26.28 < DHCP Request
    26.28 > DHCP ACK

Looking at the log 2022.05..2022.08-rc1, I identified the regression to
be in commit c343e01ac4908f76520cf9a405ed87650e78dc62. This commit adds
the option -t1 to the udhcpc command, which makes it go to the
background after only one try, and has the unfortunate side effect of
introducing a 20-second delay.

With this patch applied, the lease is acquired much faster:

    03.26 < DHCP Discover
    06.26 > DHCP Offer
    09.28 < DHCP Discover
    09.29 > DHCP Offer
    09.29 < DHCP Request
    09.29 > DHCP ACK

Regards,

Edgar.

 package/busybox/busybox.config | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package/busybox/busybox.config b/package/busybox/busybox.config
index 2409cbcce1..137e44c870 100644
--- a/package/busybox/busybox.config
+++ b/package/busybox/busybox.config
@@ -1022,7 +1022,7 @@ CONFIG_UDHCP_DEBUG=0
 CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS=80
 CONFIG_FEATURE_UDHCP_RFC3397=y
 CONFIG_FEATURE_UDHCP_8021Q=y
-CONFIG_IFUPDOWN_UDHCPC_CMD_OPTIONS="-t1 -b -R -O search"
+CONFIG_IFUPDOWN_UDHCPC_CMD_OPTIONS="-t1 -A3 -b -R -O search"
 
 #
 # Print Utilities
-- 
2.25.1
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Re: [Buildroot] [PATCH 1/1] package/busybox: speed up DHCP lease acquisition

[Angelo Compagnucci]

Il giorno sab 13 ago 2022 alle ore 22:53 Edgar Bonet
<bonet@grenoble.cnrs.fr> ha scritto:
>
> Commit c343e01ac4908f76520cf9a405ed87650e78dc62 made udhcpc send a
> single DHCP request (instead of 3) before going to the background, thus
> speeding up the boot process if the DHCP lease is not obtained
> immediately. Unfortunately, this can also slow down the acquisition of
> the lease as, after going to the background, udhcpc waits for 20 seconds
> (instead of 3) before retrying.
>
> Speed up the lease acquisition by setting the retry timeout to 3
> seconds.
>
> Signed-off-by: Edgar Bonet <bonet@grenoble.cnrs.fr>
> ---
> Hello!
>
> While testing 2022.08-rc1 with acmesystems_acqua_a5_512mb_defconfig on a
> real Acqua board (and Ubuntu 20.04 host), I noticed that my board became
> very slow in getting a DHCP lease, which was a fast process on 2022.05.
> Wireshark showed the following DHCP traffic ("<" = received from the
> board, ">" = sent to the board):
>
>     time (s)  packet
>     ---------------------
>     03.24 < DHCP Discover
>     06.24 > DHCP Offer
>     26.28 < DHCP Discover
>     26.28 > DHCP Offer
>     26.28 < DHCP Request
>     26.28 > DHCP ACK
>
> Looking at the log 2022.05..2022.08-rc1, I identified the regression to
> be in commit c343e01ac4908f76520cf9a405ed87650e78dc62. This commit adds
> the option -t1 to the udhcpc command, which makes it go to the
> background after only one try, and has the unfortunate side effect of
> introducing a 20-second delay.
>
> With this patch applied, the lease is acquired much faster:
>
>     03.26 < DHCP Discover
>     06.26 > DHCP Offer
>     09.28 < DHCP Discover
>     09.29 > DHCP Offer
>     09.29 < DHCP Request
>     09.29 > DHCP ACK
>
> Regards,

While I'm ok with this patch, I suggest checking why obtaining the
lease fails on your board on the first try.

The intent of adding -t1 was to speed up the boot process not wasting
time waiting foreground: this can be generically applied to any board:
the network cable could be unplugged and this shouldn't affect the
boot process time.

The patch you propose here instead tries to solve a problem you have
with your board: the board doesn't obtain the lease timely (first try)
and then you want a faster retry.
I think this is not generic enough to be acceptable for all the
boards, you can solve this problem easily on your local busybox
defconfig.

Anyway I'm not against changing the default background retry timeout
if this is not harming other users.

>
> Edgar.
>
>  package/busybox/busybox.config | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/package/busybox/busybox.config b/package/busybox/busybox.config
> index 2409cbcce1..137e44c870 100644
> --- a/package/busybox/busybox.config
> +++ b/package/busybox/busybox.config
> @@ -1022,7 +1022,7 @@ CONFIG_UDHCP_DEBUG=0
>  CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS=80
>  CONFIG_FEATURE_UDHCP_RFC3397=y
>  CONFIG_FEATURE_UDHCP_8021Q=y
> -CONFIG_IFUPDOWN_UDHCPC_CMD_OPTIONS="-t1 -b -R -O search"
> +CONFIG_IFUPDOWN_UDHCPC_CMD_OPTIONS="-t1 -A3 -b -R -O search"
>
>  #
>  # Print Utilities
> --
> 2.25.1
> _______________________________________________
> buildroot mailing list
> buildroot@buildroot.org
> https://lists.buildroot.org/mailman/listinfo/buildroot



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Re: [Buildroot] [PATCH 1/1] package/busybox: speed up DHCP lease acquisition

[Edgar Bonet]

Hi!

On 13/08/2022 23:36, Angelo Compagnucci wrote:
> I suggest checking why obtaining the lease fails on your board on the
> first try

What Wireshark shows, is that on the first try the host took three
seconds to respond to the DHCP request. Three seconds is just the
timeout of udhcpc, so it had just given up waiting for the response.
This does not seem to be board-specific to me.

I do not know why the hosts does not respond faster. It is a quite
vanilla Ubuntu 20.04, with the Ethernet port configured as “Shared to
other computers”.

Regards,

Edgar.
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Re: [Buildroot] [PATCH 1/1] package/busybox: speed up DHCP lease acquisition

[Yann E. MORIN]

Edgar, All,

On 2022-08-13 22:53 +0200, Edgar Bonet spake thusly:
> Commit c343e01ac4908f76520cf9a405ed87650e78dc62 made udhcpc send a
> single DHCP request (instead of 3) before going to the background, thus
> speeding up the boot process if the DHCP lease is not obtained
> immediately. Unfortunately, this can also slow down the acquisition of
> the lease as, after going to the background, udhcpc waits for 20 seconds
> (instead of 3) before retrying.
> 
> Speed up the lease acquisition by setting the retry timeout to 3
> seconds.
> 
> Signed-off-by: Edgar Bonet <bonet@grenoble.cnrs.fr>

I was unsure whether to consider this a fix or a new feature, but I
think we can really consider it a fix for a regresion, so: applied to
master, thanks.

And thanks for the detailed example!

Regards,
Yann E. MORIN.

> ---
> Hello!
> 
> While testing 2022.08-rc1 with acmesystems_acqua_a5_512mb_defconfig on a
> real Acqua board (and Ubuntu 20.04 host), I noticed that my board became
> very slow in getting a DHCP lease, which was a fast process on 2022.05.
> Wireshark showed the following DHCP traffic ("<" = received from the
> board, ">" = sent to the board):
> 
>     time (s)  packet
>     ---------------------
>     03.24 < DHCP Discover
>     06.24 > DHCP Offer
>     26.28 < DHCP Discover
>     26.28 > DHCP Offer
>     26.28 < DHCP Request
>     26.28 > DHCP ACK
> 
> Looking at the log 2022.05..2022.08-rc1, I identified the regression to
> be in commit c343e01ac4908f76520cf9a405ed87650e78dc62. This commit adds
> the option -t1 to the udhcpc command, which makes it go to the
> background after only one try, and has the unfortunate side effect of
> introducing a 20-second delay.
> 
> With this patch applied, the lease is acquired much faster:
> 
>     03.26 < DHCP Discover
>     06.26 > DHCP Offer
>     09.28 < DHCP Discover
>     09.29 > DHCP Offer
>     09.29 < DHCP Request
>     09.29 > DHCP ACK
> 
> Regards,
> 
> Edgar.
> 
>  package/busybox/busybox.config | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/package/busybox/busybox.config b/package/busybox/busybox.config
> index 2409cbcce1..137e44c870 100644
> --- a/package/busybox/busybox.config
> +++ b/package/busybox/busybox.config
> @@ -1022,7 +1022,7 @@ CONFIG_UDHCP_DEBUG=0
>  CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS=80
>  CONFIG_FEATURE_UDHCP_RFC3397=y
>  CONFIG_FEATURE_UDHCP_8021Q=y
> -CONFIG_IFUPDOWN_UDHCPC_CMD_OPTIONS="-t1 -b -R -O search"
> +CONFIG_IFUPDOWN_UDHCPC_CMD_OPTIONS="-t1 -A3 -b -R -O search"
>  
>  #
>  # Print Utilities
> -- 
> 2.25.1
> _______________________________________________
> buildroot mailing list
> buildroot@buildroot.org
> https://lists.buildroot.org/mailman/listinfo/buildroot

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Re: [Buildroot] [PATCH 1/1] package/busybox: speed up DHCP lease acquisition

[Yann E. MORIN]

Edgar, Angelo, All,

On 2022-08-14 00:25 +0200, Edgar Bonet spake thusly:
> On 13/08/2022 23:36, Angelo Compagnucci wrote:
> > I suggest checking why obtaining the lease fails on your board on the
> > first try
> 
> What Wireshark shows, is that on the first try the host took three
> seconds to respond to the DHCP request. Three seconds is just the
> timeout of udhcpc, so it had just given up waiting for the response.
> This does not seem to be board-specific to me.

I really pondered this and Angelo's concerns, but in the end I too
believe this is not board-specific, and is a welcome fix, so I applied
to master.

Regards,
Yann E. MORIN.

> I do not know why the hosts does not respond faster. It is a quite
> vanilla Ubuntu 20.04, with the Ethernet port configured as “Shared to
> other computers”.
> 
> Regards,
> 
> Edgar.
> _______________________________________________
> buildroot mailing list
> buildroot@buildroot.org
> https://lists.buildroot.org/mailman/listinfo/buildroot

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 561 099 427 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'
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