Re: [PATCH net-next v2] ipv6: don't generate link-local addr in random or privacy mode

On 11/15/21 11:09 PM, Rocco Yue wrote:

In the 3GPP TS 29.061, here is a description as follows:
"In order to avoid any conflict between the link-local address
of the MS and that of the GGSN, the Interface-Identifier used by
the MS to build its link-local address shall be assigned by the
GGSN. The GGSN ensures the uniqueness of this Interface-Identifier.
The MT shall then enforce the use of this Interface-Identifier by
the TE"

In other words, in the cellular network, GGSN determines whether
to reply a solicited RA message by identifying the bottom 64 bits
of the source address of the received RS message. Therefore,
cellular network device's ipv6 link-local address should be set
as the format of fe80::(GGSN assigned IID).

To meet the above spec requirement, this patch adds two new
addr_gen_mode:

1) IN6_ADDR_GEN_MODE_STABLE_PRIVACY_NO_LLA, this mode is suitable
for cellular networks that support RFC7217. In this mode, the
kernel doesn't generate a link-local address for the cellular
NIC, and generates an ipv6 stable privacy global address after
receiving the RA message.

2) IN6_ADDR_GEN_MODE_RANDOM_NO_LLA, in this mode, the kernel
doesn't generate a link-local address for the cellular NIC,
and will use the bottom 64 bits of the link-local address(same
as the IID assigned by GGSN) to form an ipv6 global address
after receiveing the RA message.

Signed-off-by: Rocco Yue <redacted>
---
v1->v2: Add new addr_gen_mode instead of adding a separate sysctl.

v1 link:
https://patchwork.kernel.org/patch/12353465

---
 include/uapi/linux/if_link.h       |  2 ++
 net/ipv6/addrconf.c                | 22 ++++++++++++++++------
 tools/include/uapi/linux/if_link.h |  2 ++
 3 files changed, 20 insertions(+), 6 deletions(-)

Reviewed-by: David Ahern <dsahern@kernel.org>

you should add tests under tools/testing/selftests/net.