Re: [PATCH] dhcpv6: support rapid commit dhcp6 option

Thank you for the reviewing. Addressed the comments in patch V2.

Thanks,
-Yuxiao

On Tue, Aug 25, 2026 at 6:19 AM Jerome Forissier <[email protected]>
wrote:

> Hi Yuxiao,
>
> Two minor comments below. Thanks!
>
> On 19/08/2026 21:10, Yuxiao Zhang wrote:
> > Support rapid commit option code 14 which bypass the advertise and
> > request state. The option is enabled by DHCP6_RAPID_COMMIT.
> >
> > Signed-off-by: Yuxiao Zhang <[email protected]>
> > ---
> >
> >  cmd/Kconfig  |  8 ++++++++
> >  net/dhcpv6.c | 39 ++++++++++++++++++++++++++++++++-------
> >  net/dhcpv6.h |  2 ++
> >  3 files changed, 42 insertions(+), 7 deletions(-)
> >
> > diff --git a/cmd/Kconfig b/cmd/Kconfig
> > index ff90a87024c..b3cf3a6d8b6 100644
> > --- a/cmd/Kconfig
> > +++ b/cmd/Kconfig
> > @@ -1996,6 +1996,14 @@ config DHCP6_ENTERPRISE_ID
> >       int "Enterprise ID to send in DHCPv6 Vendor Class Option"
> >       default 0
> >
> > +config DHCP6_RAPID_COMMIT
> > +     bool "Request Rapid Commit (2-message exchange) from DHCPv6 server"
> > +     default n
> > +     help
> > +       Request the Rapid Commit option (option 14) in DHCPv6 Solicit
> > +       messages to enable a 2-message exchange (Solicit-Reply) rather
> > +       than the default 4-message exchange.
> > +
> >  endif
> >
> >  config BOOTP_MAY_FAIL
> > diff --git a/net/dhcpv6.c b/net/dhcpv6.c
> > index 640f089a2e1..1e51e6de256 100644
> > --- a/net/dhcpv6.c
> > +++ b/net/dhcpv6.c
> > @@ -115,6 +115,9 @@ static int dhcp6_add_option(int option_id, uchar
> *pkt)
> >
> >               opt_len = sizeof(struct dhcp6_option_ia_na);
> >               break;
> > +     case DHCP6_OPTION_RAPID_COMMIT:
> > +             opt_len = 0;
> > +             break;
> >       case DHCP6_OPTION_ORO:
> >               oro_opt = (struct dhcp6_option_oro *)dhcp_option_start;
> >               oro_opt->req_option_code[num_oro++] =
> htons(DHCP6_OPTION_OPT_BOOTFILE_URL);
> > @@ -194,6 +197,8 @@ static void dhcp6_send_solicit_packet(void)
> >       pkt += dhcp6_add_option(DHCP6_OPTION_ELAPSED_TIME, pkt);
> >       pkt += dhcp6_add_option(DHCP6_OPTION_IA_NA, pkt);
> >       pkt += dhcp6_add_option(DHCP6_OPTION_ORO, pkt);
> > +     if (IS_ENABLED(CONFIG_DHCP6_RAPID_COMMIT))
> > +             pkt += dhcp6_add_option(DHCP6_OPTION_RAPID_COMMIT, pkt);
> >       if (CONFIG_DHCP_PXE_CLIENTARCH != 0xFF)
> >               pkt += dhcp6_add_option(DHCP6_OPTION_CLIENT_ARCH_TYPE,
> pkt);
> >       pkt += dhcp6_add_option(DHCP6_OPTION_VENDOR_CLASS, pkt);
> > @@ -448,6 +453,12 @@ static void dhcp6_parse_options(uchar *rx_pkt,
> unsigned int len)
> >                       }
> >                       sm_params.rx_status.preference = *option_ptr;
> >                       break;
> > +             case DHCP6_OPTION_RAPID_COMMIT:
> > +                     if (IS_ENABLED(CONFIG_DHCP6_RAPID_COMMIT)) {
>
> option_len != 0 should probably be rejected here
>
> > +                             debug("DHCP6_OPTION_RAPID_COMMIT FOUND\n");
> > +                             sm_params.rx_status.rapid_commit_found =
> true;
> > +                     }
> > +                     break;
> >               default:
> >                       debug("Unknown Option ID: %d, skipping parsing\n",
> >                             ntohs(option_hdr->option_id));
> > @@ -618,14 +629,28 @@ static void dhcp6_state_machine(bool timeout,
> uchar *rx_pkt, unsigned int len)
> >               break;
> >       case DHCP6_SOLICIT:
> >               if (!timeout) {
> > -                     /* check the rx packet and determine if we can
> transition to next
> > -                      * state.
> > -                      */
> > -                     if (dhcp6_check_advertise_packet(rx_pkt, len))
> > -                             return;
> > +                     struct dhcp6_hdr *dhcp6_hdr = (struct dhcp6_hdr
> *)rx_pkt;
> > +
> > +                     if (IS_ENABLED(CONFIG_DHCP6_RAPID_COMMIT) &&
> > +                         dhcp6_hdr && dhcp6_hdr->msg_type ==
> DHCP6_MSG_REPLY) {
>
> dhcp6_hdr is necessarily non-NULL here, so please drop "dhcp6_hdr &&"
>
> > +                             if (dhcp6_check_reply_packet(rx_pkt, len))
> > +                                     return;
> > +                             if
> (!sm_params.rx_status.rapid_commit_found) {
> > +                                     debug("[DHCPv6] REPLY received
> without Rapid Commit option, ignoring\n");
> > +                                     return;
> > +                             }
> > +                             debug("REPLY (Rapid Commit) good,
> transition to DONE\n");
> > +                             sm_params.next_state = DHCP6_DONE;
> > +                     } else {
> > +                             /* check the rx packet and determine if we
> can transition to next
> > +                              * state.
> > +                              */
> > +                             if (dhcp6_check_advertise_packet(rx_pkt,
> len))
> > +                                     return;
> >
> > -                     debug("ADVERTISE good, transition to REQUEST\n");
> > -                     sm_params.next_state = DHCP6_REQUEST;
> > +                             debug("ADVERTISE good, transition to
> REQUEST\n");
> > +                             sm_params.next_state = DHCP6_REQUEST;
> > +                     }
> >               } else if (sm_params.retry_cnt == 1)  {
> >                       /* If a server UID was received in the first
> SOLICIT period
> >                        * transition to REQUEST
> > diff --git a/net/dhcpv6.h b/net/dhcpv6.h
> > index d41a3c30615..49f20390730 100644
> > --- a/net/dhcpv6.h
> > +++ b/net/dhcpv6.h
> > @@ -24,6 +24,7 @@
> >  #define DHCP6_OPTION_PREFERENCE              7
> >  #define DHCP6_OPTION_ELAPSED_TIME    8
> >  #define DHCP6_OPTION_STATUS_CODE     13
> > +#define DHCP6_OPTION_RAPID_COMMIT    14
> >  #define DHCP6_OPTION_OPT_BOOTFILE_URL        59
> >  #define DHCP6_OPTION_OPT_BOOTFILE_PARAM      60
> >  #define DHCP6_OPTION_SOL_MAX_RT              82
> > @@ -152,6 +153,7 @@ struct dhcp6_rx_pkt_status {
> >       enum dhcp6_status       ia_status_code;
> >       enum dhcp6_status       status_code;
> >       u8                      preference;
> > +     bool                    rapid_commit_found;
> >  };
> >
> >  /**
> > ---
> > base-commit: 527115ef6783cec49e5610c523c124b399011361
> > branch: main
> >
>
> --
> Jerome
>