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MFC sys/netinet6: Implement RFC 7217 (private stable addresses)
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Authored by madpilot on Dec 27 2025, 10:16 PM.

Details

Reviewers

cognet
glebius
hrs
jhibbits
jtl
zlei
linnemannr_gmail.com
kp
pouria
olivier

Commits

rGc20f5fd44322: ifconfig.8: Start new sentence on new line
rG76cd2807fc3a: sys/netinet6: Fix ABI breakage introduced with RFC 7217 support

Summary

I'd like to MFC my RFC 7217 implementation to 15-stable.

As suggested by @zarychtam_plan-b.pwste.edu.pl I'm also including SLAAC patches ([1] and followup fix [2]) from @linnemannr_gmail.com, to allow a clean merge without conflicts.

I think this is the cleanest choice, otherwise I could merge my patches only fixing conflicts, but then there would be further conflicts if [1] and [2] are to be merged later.

I'm including everyone who approved the previous patches as reviewers, plus @linnemannr_gmail.com and @kp as author and commiter of the extra patches I'm planning to bring along.

Also, I plan to merge each commit as a single cherry pick and push them in one go. Looks to me like the best way, if merging them in a single commit is preferred please let me know.

Test Plan

I've tested the patch in bhyve VMs and everything looks fine.

I'm also leveraging this code daily on head.

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Passed

Unit

No Test Coverage

Build Status

Buildable 70048
Build 66931: arc lint + arc unit

Event Timeline

madpilot created this revision.Dec 27 2025, 10:16 PM

Herald added subscribers: ziaee, melifaro, imp. · View Herald TranscriptDec 27 2025, 10:16 PM

madpilot requested review of this revision.Dec 27 2025, 10:16 PM

Harbormaster completed remote builds in B69487: Diff 168651.Dec 27 2025, 10:16 PM

madpilot retitled this revision from MFC sys/netinet6: Implement RFC 7217 (privat estable addresses) to MFC sys/netinet6: Implement RFC 7217 (private stable addresses).Dec 27 2025, 10:17 PM

Forgot to add references:

[1] 9e792f7ef7298080c058fbc2d36a4e60e596dae9
[2] f9fc93690aef7a56f62a051de6231fe2af699728

ALso, I plan to merge each commit as a single cherry pick and push them in one go. Looks to me like the best way, if merging them in a single commit is preferred please let me know.

Given this is a new feature, I think it will be much more clean to merge all related commits into a single one when MFCing.

madpilot edited the summary of this revision. (Show Details)Dec 30 2025, 5:22 PM

In D54382#1242898, @zlei wrote:

Also, I plan to merge each commit as a single cherry pick and push them in one go. Looks to me like the best way, if merging them in a single commit is preferred please let me know.

Given this is a new feature, I think it will be much more clean to merge all related commits into a single one when MFCing.

Thanks for the feedback. If this is the cnsensus I can go this way, using the commit message from 31ec8b6407fdd5a87d70265762457c67ce618283 but adding the required tags and "cherry picked" lines. And a comment about the other related commits.

From a testing perspective, I can confirm that the solution has been working well on stable/15 for quite some time on a laptop and several desktops. I recently cherry-picked it at work onto our build machine and started testing it on servers running stable/15 as well, although only a small subset of those systems use EUI-64–based IPv6 addressing.

I’m not convinced that squashing these commits would add much value. None of them introduces critical breakage - the system will never panic. The MFC workflow is well known and clear, and bisecting can always be properly done against not only the main branch.

In D54382#1242817, @madpilot wrote:

Forgot to add references:

[1] 9e792f7ef7298080c058fbc2d36a4e60e596dae9

This is a behaviour change, which is why I initially didn't mark it as an MFC candidate.
That said, it's very limited in scope, and only allows users to do new things, I don't expect this to break any existing setups, so there should be relatively little risk to including it.

[2] f9fc93690aef7a56f62a051de6231fe2af699728

This is a fix to the above, so either take both or neither.

I had some time to test the below{1} merge on stable/15 following the traditional, still recommended upgrade path with intermediate reboot (install kernel, reboot, install world, reboot).
I hereby report that the stable/15 system with IPv6 EUI-64–based primary address and IPv6 static address configured as alias0 encountered no problems after the first and second reboot. Moreover, with stableddress enabled in the loader.conf[2], the system did not encounter any issues either and after the first reboot system was already following RFC 7217 requirements. Thus, it was proven that even if stableaddr will become the default at some point, the ABI will not be broken, and old ifconfig(8) will be able to take care of interface addressing.

! In D54382#1242898, @zlei wrote:
Given this is a new feature, I think it will be much more clean to merge all related commits into a single one when MFCing.

When I was testing the initial implementation, I believed that ABI breakage must happen, but it was a wrong assumption. The above tests have proven that squashing commits

sys/netinet6: Implement RFC 7217 (cherry picked from commit 31ec8b6407fdd5a87d70265762457c67ce618283) and
sys/netinet6: Fix ABI breakage introduced with RFC 7217 support (cherry picked from commit 0ec13430c583830cc4d29640787e2d154b140e31)

could be valuable and appreciated.

[1]:

sys/netinet6: Fix SLAAC for interfaces with no /64 LL address (cherry picked from commit 9e792f7ef7298080c058fbc2d36a4e60e596dae9)
sys/netinet6: Implement RFC 7217 (cherry picked from commit 31ec8b6407fdd5a87d70265762457c67ce618283)
sys/netinet6: Fix ABI breakage introduced with RFC 7217 support (cherry picked from commit 0ec13430c583830cc4d29640787e2d154b140e31)
sys/netinet6: Use atomic(9) for dad_failures counter (cherry picked from commit 0c94dc9da7c238603e43c55ca6da64c417fc2204)
sys/netinet6: fix memory corruption in in6_ifadd (cherry picked from commit f9fc93690aef7a56f62a051de6231fe2af699728)

[2]:

net.inet6.ip6.use_stableaddr="1"
net.inet6.ip6.stableaddr_netifsource="2"

Updating this review to only inlcude my commits.

This should simplify the process and allow me to merge the individual commits in one go.

Harbormaster completed remote builds in B70048: Diff 170219.Jan 21 2026, 9:28 PM

JFYI: this patch will need some trivial adjustments after I land https://reviews.freebsd.org/D54725

In D54382#1253065, @glebius wrote:

JFYI: this patch will need some trivial adjustments after I land https://reviews.freebsd.org/D54725

Thanks for the heads up!

I'll be updating and testing again after you MFC that.

In D54382#1253065, @glebius wrote:

JFYI: this patch will need some trivial adjustments after I land https://reviews.freebsd.org/D54725

Actually wouldn't merging this change make merging your change to stable/15 easier?

Not being a src committer I was waiting for an approval to do this merge.

I don't plan to merge my changes.

pouria added a subscriber: pouria.Jan 27 2026, 12:09 AM

zarychtam_plan-b.pwste.edu.pl added a reviewer: pouria.Jan 27 2026, 9:32 AM

zarychtam_plan-b.pwste.edu.pl added a reviewer: olivier.Jan 27 2026, 2:25 PM

Fix some style(9) nits.

sys/netinet6/in6_ifattach.c
160
180
183
252
255
270
316
377
385–389

Fix manual style/warning nits

sbin/ifconfig/ifconfig.8
1011–1012	mandoc: STYLE: input text line longer than 80 bytes:
1016–1018	mandoc: STYLE: input text line longer than 80 bytes: + use Xr for loader.conf(5)
1022	mandoc: STYLE: input text line longer than 80 bytes:
1027	mandoc: STYLE: no blank before trailing delimiter...
1028	mandoc: WARNING: missing -width in -tag list, using 6n: Bl -tag
1035–1036	mandoc: WARNING: skipping paragraph macro: Pp before It

ziaee added inline comments.Jan 27 2026, 10:16 PM

sbin/ifconfig/ifconfig.8
1011–1012	You don't have to, but it's very nice to wrap at 72 so it's easier on people who use 80 character consoles with line numbering. For manuals, I like to try to wrap early to keep greppable phrases together.

pouria added inline comments.Jan 27 2026, 10:31 PM

sbin/ifconfig/ifconfig.8
1011–1012	Thanks! I don't like `mandoc` to complain about anything because I don't understand its syntax. it’s like it’s speaking another language :)

Please take into consideration that the changes discussed in this review are already present in the main branch (16.0-CURRENT). Escalating demands here is pointless. If the man page requires fixes, the right approach would be to fix it in the main branch and then MFC those changes to stable/15 (if this review ever lands in stable/15).

The same, in my opinion, applies to the rest of the code - the more that can be done via conflict-free cherry-picking, the better for the FreeBSD project.

By the way, I am still testing this in our stable/15 branch at work on servers running in production, as well as on my own laptop and PC. So far, so good.

Please fixs those on CURRENT. For this MFC, LGTM.

This revision is now accepted and ready to land.Jan 28 2026, 7:39 AM

Updated the review to include recent commits with style fixes.

This revision now requires review to proceed.Feb 9 2026, 8:38 PM

Harbormaster completed remote builds in B70561: Diff 171596.Feb 9 2026, 8:38 PM

Can you please rebase? There is no longer ND_IFINFO().

sys/netinet6/in6_ifattach.c
194–195	Please use `uint8_t`.

Thanks for your comments,

In D54382#1263614, @glebius wrote:

Can you please rebase? There is no longer ND_IFINFO().

This is a request for an MFC against stable/15 The code already committed in head was modified to remove ND_IFINFO(), but thise changes are not in stable/15, so ND_IFINFO is still there. Or maybe I'm misunderstanding your request.

sys/netinet6/in6_ifattach.c
194–195	Being an MFC request I think I should first change this in head and then cherry-pick such a commit. I can do that, in case you want me to, can I use this request as an implicit approval for that very commit?

No objection for MFC. Neither encouragement, though :)

sys/netinet6/in6_ifattach.c
194–195	I'm sorry, I didn't notice the review is about MFC.

This revision is now accepted and ready to land.Feb 15 2026, 8:23 PM

Closed by commit rG76cd2807fc3a: sys/netinet6: Fix ABI breakage introduced with RFC 7217 support (authored by madpilot). · Explain WhyFeb 16 2026, 5:30 PM

This revision was automatically updated to reflect the committed changes.

madpilot mentioned this in rG865e0b20ca3c: sys/netinet6: Implement RFC 7217.

madpilot added a commit: rG76cd2807fc3a: sys/netinet6: Fix ABI breakage introduced with RFC 7217 support.

madpilot mentioned this in rG4c7357aaf5d2: sys/netinet6: Use atomic(9) for dad_failures counter.

madpilot mentioned this in rG20294a77a8d4: netinet6: Fix my style issues.

madpilot added a commit: rGc20f5fd44322: ifconfig.8: Start new sentence on new line.

Heads up warning: these code paths are very likely to be touched by an ILNPv6 merge (RFC 6740 and up). @rgrimes and I need to have a chat first.

In D54382#1264959, @bms wrote:

Heads up warning: these code paths are very likely to be touched by an ILNPv6 merge (RFC 6740 and up). @rgrimes and I need to have a chat first.

Given this is an MFC from head to 15 it has precedence over any external ILNPv6 work at this point in time. I'll already have to deal with these changes as I migrate the ILNPv6 code from its current 14.3 base to -HEAD