Re: [PATCH v2 2/2] dhcpv6: Inject custom options into DHCPv6 replies

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 18 Jun 2026 17:35:29 +0530
Anshu Kumari <anskuma@redhat.com> wrote:

> Append user-specified options from --dhcpv6-opt to DHCPv6 reply
> messages.  Options are parsed from the stored string value at reply
> time using dhcpv6_opt_parse(), and skipped with a debug message if
> they exceed the available space.
> 
> Link: https://bugs.passt.top/show_bug.cgi?id=192
> Signed-off-by: Anshu Kumari <anskuma@redhat.com>
> ---
> v2:
>   - Updated dhcpv6_custom_opts_fill() to parse str at reply time
>     using dhcpv6_opt_parse() instead of copying cached val/len.
> ---
>  dhcpv6.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/dhcpv6.c b/dhcpv6.c
> index 1e1dd0d..6b1e90b 100644
> --- a/dhcpv6.c
> +++ b/dhcpv6.c
> @@ -748,6 +748,49 @@ static size_t dhcpv6_client_fqdn_fill(const struct iov_tail *data,
>  	return offset + sizeof(struct opt_hdr) + opt_len;
>  }
>  
> +/**
> + * dhcpv6_custom_opts_fill() - Append user-specified custom options to reply
> + * @c:		Execution context
> + * @buf:	Response message buffer
> + * @offset:	Current offset in buffer
> + *
> + * Return: updated offset after appending custom options
> + */
> +static size_t dhcpv6_custom_opts_fill(const struct ctx *c,
> +				      char *buf, int offset)
> +{
> +	int i;
> +
> +	for (i = 0; i < c->dhcpv6_opts_count; i++) {
> +		uint16_t code = c->dhcpv6_opts[i].code;
> +		struct opt_hdr *hdr;
> +		uint8_t val[255];

This should be UINT16_MAX. Other than that, this looks good to me,
except for pending comments from David and also my considerations on
top of that.

-- 
Stefano