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[34.48.33.21]) by smtp.gmail.com with UTF8SMTPSA id 956f58d0204a3-649960639e2sm2772415d50.1.2026.01.29.11.01.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Jan 2026 11:01:12 -0800 (PST) Date: Thu, 29 Jan 2026 14:01:11 -0500 From: Willem de Bruijn To: Justin Iurman , Willem de Bruijn , Tom Herbert , davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org Message-ID: In-Reply-To: <60fb02d8-77ca-457b-be24-33a3cc7b344b@gmail.com> References: <20260126194826.236075-1-tom@herbertland.com> <20260126194826.236075-3-tom@herbertland.com> <60fb02d8-77ca-457b-be24-33a3cc7b344b@gmail.com> Subject: Re: [PATCH net-next v5 2/7] ipv6: Cleanup IPv6 TLV definitions Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Justin Iurman wrote: > On 1/29/26 06:30, Willem de Bruijn wrote: > > Tom Herbert wrote: > >> Move IPV6_TLV_TNL_ENCAP_LIMIT to uapi/linux/in6.h to be with the rest > >> of the TLV definitions. Label each of the TLV definitions as to whether > >> they are a Hop-by-Hop option, Destination option, or both. > >> > >> Signed-off-by: Tom Herbert > >> --- > >> include/uapi/linux/in6.h | 21 ++++++++++++++------- > >> include/uapi/linux/ip6_tunnel.h | 1 - > >> 2 files changed, 14 insertions(+), 8 deletions(-) > >> > >> diff --git a/include/uapi/linux/in6.h b/include/uapi/linux/in6.h > >> index 5a47339ef7d7..438283dc5fde 100644 > >> --- a/include/uapi/linux/in6.h > >> +++ b/include/uapi/linux/in6.h > >> @@ -140,14 +140,21 @@ struct in6_flowlabel_req { > >> > >> /* > >> * IPv6 TLV options. > >> + * > >> + * Hop-by-Hop and Destination options share the same number space. > >> + * For each option below whether it is a Hop-by-Hop option or > >> + * a Destination option is indicated by HBH or DestOpt. > >> */ > >> -#define IPV6_TLV_PAD1 0 > >> -#define IPV6_TLV_PADN 1 > >> -#define IPV6_TLV_ROUTERALERT 5 > >> -#define IPV6_TLV_CALIPSO 7 /* RFC 5570 */ > >> -#define IPV6_TLV_IOAM 49 /* RFC 9486 */ > >> -#define IPV6_TLV_JUMBO 194 > >> -#define IPV6_TLV_HAO 201 /* home address option */ > >> +#define IPV6_TLV_PAD1 0 /* HBH or DestOpt */ > >> +#define IPV6_TLV_PADN 1 /* HBH or DestOpt */ > >> +#define IPV6_TLV_TNL_ENCAP_LIMIT 4 /* RFC 2473, DestOpt */ > >> +#define IPV6_TLV_ROUTERALERT 5 /* HBH */ > >> +#define IPV6_TLV_CALIPSO 7 /* RFC 5570, HBH */ > >> +#define IPV6_TLV_IOAM 49 /* RFC 9486, HBH or Destopt > >> + * IOAM sent and rcvd as HBH > > > > Explicit labeling with HBH or Destopt is quite informative. > > > > Does this mean that IPV6_TLV_IOAM should also be accepted in ip6_parse_tlv > > in the Destopt branch? RFC 9486 indeed did reserve a number. > > Nope, not right now. The only IOAM option currently implemented in the > kernel is the Pre-allocated Trace, which uses a Hop-by-Hop option. It > wouldn't make sense to have it in a Destination option, although you > could (i.e., it's not forbidden, just weird). Actually, the only IOAM > option that would make sense to carry in a Destination Option is the > Edge-to-Edge (E2E), but it's not implemented in the kernel. Should it be > implemented at some point, then yes, you'd have IPV6_TLV_IOAM in the > Destopt branch as well. Sounds great. Thanks for that context.