The upcoming (and nearly finalized): https://datatracker.ietf.org/doc/draft-collink-6man-pio-pflag/ will update the IPv6 RA to include a new flag in the PIO field, which will serve as a hint to perform DHCPv6-PD.

As we don't want DHCPv6 related logic inside the kernel, this piece of information needs to be exposed to userspace. The simplest option is to simply expose the entire PIO through the already existing mechanism.

Even without this new flag, the already existing PIO R (router address) flag (from RFC6275) cannot AFAICT be handled entirely in kernel, and provides useful information that should be exposed to userspace (the router's global address, for use by Mobile IPv6).

Also cc'ing stable@ for inclusion in LTS, as while technically this is not quite a bugfix, and instead more of a feature, it is absolutely trivial and the alternative is manually cherrypicking into all Android Common Kernel trees - and I know Greg will ask for it to be sent in via LTS instead...

Cc: Jen Linkova furry@google.com Cc: Lorenzo Colitti lorenzo@google.com Cc: David Ahern dsahern@gmail.com Cc: David S. Miller davem@davemloft.net Cc: Eric Dumazet edumazet@google.com Cc: YOSHIFUJI Hideaki / 吉藤英明 yoshfuji@linux-ipv6.org Cc: stable@vger.kernel.org Signed-off-by: Maciej Żenczykowski maze@google.com --- net/ipv6/ndisc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 18634ebd20a4..a42be96ae209 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -197,7 +197,8 @@ static struct nd_opt_hdr *ndisc_next_option(struct nd_opt_hdr *cur, static inline int ndisc_is_useropt(const struct net_device *dev, struct nd_opt_hdr *opt) { - return opt->nd_opt_type == ND_OPT_RDNSS || + return opt->nd_opt_type == ND_OPT_PREFIX_INFO || + opt->nd_opt_type == ND_OPT_RDNSS || opt->nd_opt_type == ND_OPT_DNSSL || opt->nd_opt_type == ND_OPT_CAPTIVE_PORTAL || opt->nd_opt_type == ND_OPT_PREF64 ||