gnrc_ipv6_nib/SLAAC: rfc8981 temporary address (privacy extensions) #20369

xnumad · 2024-02-11T01:30:09Z

Contribution description

This implements RFC8981.

Design

The RFC describes an implementation where lifetimes are associated directly with an address. This is not the case in GNRC, where lifetimes are associated with a prefix (prefix list - https://datatracker.ietf.org/doc/html/rfc4861#section-5.1). This PR therefore adjusts the logic to be compatible with this design, while of course still following all the RFC requirements. (The adjusted logic may even be considered simpler than the one described in the RFC!)

In particular, the changes is in the logic used to implement coupling of temporary address to lifetimes of SLAAC prefix while still retaining maximum lifetimes for a temporary address:

RFC: Initial and updated values for the lifetimes of the temporary address are always derived from both the prefix lifetime as well as the lifetime limits configured for temporary addresses.
this PR: A temporary address is coupled to a new /128 (code keyword IPV6_ADDR_BIT_LEN=128) prefix to manage its maximum lifetime. (Coupling being that they are created and deleted at once.) Then, to couple the temporary address with the SLAAC prefix it was created from (so that the temporary address cannot possibly outlive the SLAAC prefix), the temporary address is deleted if the SLAAC prefix is deprecated or invalidated.

Therefore this PR considers an IP address to be temporary iff there exists a /128 prefix for it (i.e. with that address). This assumption is used throughout this implementation, in particular to determine whether an assigned address is a temporary address:
https://github.com/xnumad/RIOT/blob/15e8518d64f674d711f9e4d0fdd613617257a715/sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.c#L183
https://github.com/xnumad/RIOT/blob/15e8518d64f674d711f9e4d0fdd613617257a715/sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.c#L230
It is theoretically possible for this circumstance to interfere with other /128 prefixes in the prefix list (e.g. a PIO for exactly that /128 prefix). This conflict could be detected by using a flag (to indicate relation to temporary address usage), but otherwise not avoided unless further changing the lifetime management, e.g. separating it from the NIB prefix list or even using the RFC logic that associates lifetimes directly to an address.

--

Design decision of where to store (temp addr) regeneration event:
The regen event timer is associated with the prefix for the temporary address, because a refactor showed that it results in easier code than when storing it associated with the SLAAC prefix. (f33d2e6)

--

Other noteworthy implications of this PR:

implements the SLAAC_PREFIX_LENGTH=64 requirement of RFCs (see macro definition for RFC reference)
adds a new address flag, GNRC_NETIF_IPV6_ADDRS_FLAGS_IDGEN_RETRIES, as an easy way to associate the retry counter with the address, because the value is used again if DAD failures occur
These changes are also cherry-picked to the RFC7217 implementation at gnrc_ipv6_nib/SLAAC: rfc7217 stable privacy addresses #20370

--

RFC compatibility

All but the following requirements of the RFC are implemented:

(Requirements from section 3.3.2 do not apply because this PR uses the other algorithm, i.e. from section 3.3.1)

Disable if retry limit reached

If, after TEMP_IDGEN_RETRIES consecutive attempts, the host is unable to generate a unique temporary address, the host MUST log a system error and SHOULD NOT attempt to generate a temporary address for the given prefix for the duration of the host's attachment to the network via this interface.
Subrange list

implementations SHOULD provide a way to enable and disable generation of temporary addresses for specific prefix subranges

Currently, no such subrange list is implemented. (Although comparatively low effort to implement.)
Temporary addresses are generated for any "prefix advertised in a RA PIO with A flag set" and not for link-local addresses.
Ad-hoc toggle

In addition, a site might wish to disable the use of temporary addresses in order to simplify network debugging and operations. Consequently, implementations SHOULD provide a way for trusted system administrators to enable or disable the use of temporary addresses.

Interpreting this as the need to ad-hoc disable temporary addresses. Not fulfilled; the setting is only set through a compile-time flag and cannot be changed at runtime.
Cleanup

when an interface connects to a new (different) link, existing temporary addresses for the corresponding interface MUST be removed

Should this be added to

RIOT/sys/net/gnrc/network_layer/ipv6/nib/nib.c

Line 173 in 32d1cd9

void gnrc_ipv6_nib_iface_down(gnrc_netif_t *netif, bool send_final_ra)

?
Currently, only link-local addresses seem to be removed at all.

RIOT/sys/net/gnrc/network_layer/ipv6/nib/nib.c

Line 196 in 32d1cd9

if (ipv6_addr_is_link_local(&netif->ipv6.addrs[i])) {

I didn't find a way to test this.

Adaptability

This implementation supports Ethernet and 6LoWPAN. Supporting a new link layer only requires its REGEN_ADVANCE value to be returned by
https://github.com/xnumad/RIOT/blob/15e8518d64f674d711f9e4d0fdd613617257a715/sys/net/gnrc/netif/gnrc_netif_device_type.c#L224

The usage of IIDs which do not match the link layer address causes LOWPAN_IPHC to not be able to statelessly compress the IP address anymore. An optimization to enable compression again could be to add compression contexts (feature branch for opportunistic compression contexts: https://github.com/xnumad/RIOT/tree/feature%2Fopportunistic-compression-contexts).

Testing procedure

Add CFLAGS += -DCONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES=1 at the appropriate position in the Makefile of examples/gnrc_networking. Tested on BOARD=nrf52840dk

Output of ifconfig command is expected to contain a line with a temporary address ("TMP"), like inet6 addr: 2001:db8::6f04:c775:f9a9:dc48 scope: global VAL TMP
The temporary address is the preferred source address for the global address scope (can be tested by e.g. ping)

(And many more tests could be done)

kaspar030 · 2024-02-21T21:56:15Z

Welcome @xnumad! And thanks for your contribution. 😄
This looks quite interesting. Curious what the gnrc specialists have to say about it.

xnumad · 2024-08-26T09:42:23Z

Rebased, then dropped last commit (5d5b8c6) which was a workaround to a bug that was fixed in #20757 (hence the rebase)

xnumad · 2024-09-18T14:51:42Z

Rebased.

xnumad · 2024-09-18T14:54:16Z

Changed commit message.

Need to check for matching address rather than prefix because for a 6LN, the SLAAC prefix is never stored in the prefix list, since everything is considered off-link.

Log it

Fix time units

Slightly simplifies the coupling by moving the prefix deletion from the inner to the outer function in the call chain, when deleting a temporary address prefix: Previously: Prefix deletion calls addr deletion, which calls a prefix deletion again, which deletes the prefix, leaving the outer prefix deletion function with no prefix to delete. Now: Outer function deletes prefix before calling address deletion function, which still calls prefix deletion function, but it's this one now that doesn't have any prefix to delete.

Increases readability Was previously also needed to enable regen to work on 6LN, because a 6LN did not store SLAAC prefix prior to PR RIOT-OS#20757.

As the ta_pfx will have an NCE with unspecified next hop, 1 NCE is needed for that.

xnumad · 2025-06-18T23:56:51Z

Rebased to resolve merge conflicts

crasbe · 2025-06-19T20:32:30Z

Since this was not reviewed yet, you can probably squash your commits a bit if you want to.

riot-ci · 2025-06-19T20:52:44Z

Murdock results

✔️ PASSED

992147c Adjust for PR #20371

Success	Failures	Total	Runtime
10379	0	10379	10m:24s

Artifacts

Documentation preview

crasbe

I don't really have experience with the proposed changes or the network subsystem of RIOT in general, but below you find some general comments about the code. Nothing major, mostly style related nitpicks.

crasbe · 2025-06-19T20:35:43Z

sys/include/net/gnrc/ipv6/nib.h

+ *
+ * @see "REGEN_ADVANCE time units before" - https://www.rfc-editor.org/rfc/rfc8981.html#section-3.6
+ */
+#define GNRC_IPV6_NIB_REGEN_TEMP_ADDR       (0x4fd6U)


Suggested change

#define GNRC_IPV6_NIB_REGEN_TEMP_ADDR (0x4fd6U)

# define GNRC_IPV6_NIB_REGEN_TEMP_ADDR (0x4fd6U)

For newly added code we try to establish the indentation in preprocessor commands too, as is the case in other parts of this PR too.

crasbe · 2025-06-19T20:38:42Z

sys/include/net/gnrc/ipv6/nib/conf.h

@@ -64,7 +64,7 @@ extern "C" {
 #      endif
 #      ifndef CONFIG_GNRC_IPV6_NIB_NUMOF
         /* only needs to store default router */
-#        define CONFIG_GNRC_IPV6_NIB_NUMOF           (1)
+#        define CONFIG_GNRC_IPV6_NIB_NUMOF           (1 + IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES))


Suggested change

# define CONFIG_GNRC_IPV6_NIB_NUMOF (1 + IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES))

# if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES))

# define CONFIG_GNRC_IPV6_NIB_NUMOF (2)

# else

# define CONFIG_GNRC_IPV6_NIB_NUMOF (1)

# endif

I think this would be a better approach than mixing the boolean result of the IS_ACTIVE and an integer.

crasbe · 2025-06-19T20:38:49Z

sys/include/net/gnrc/ipv6/nib/conf.h

+ * @see [RFC 8981](https://www.rfc-editor.org/rfc/rfc8981.html)
+ */
+#ifndef CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES
+#define CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES 0


Suggested change

#define CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES 0

# define CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES 0

crasbe · 2025-06-19T20:39:31Z

sys/include/net/gnrc/netif/conf.h

+#ifndef MAX_TEMP_ADDRESSES
+#define MAX_TEMP_ADDRESSES (4)
+#endif
+#else
+#define MAX_TEMP_ADDRESSES (0)


Suggested change

#ifndef MAX_TEMP_ADDRESSES

#define MAX_TEMP_ADDRESSES (4)

#endif

#else

#define MAX_TEMP_ADDRESSES (0)

# ifndef MAX_TEMP_ADDRESSES

# define MAX_TEMP_ADDRESSES (4)

# endif

#else

# define MAX_TEMP_ADDRESSES (0)

crasbe · 2025-06-19T20:40:34Z

sys/include/net/gnrc/netif/conf.h

@@ -102,6 +102,33 @@ extern "C" {
 #define GNRC_NETIF_IPV6_RTR_ADDR   (0)
 #endif

+/**
+ * @brief Maximum assumed number of valid (preferred or deprecated) temporary addresses.
+ * (see _nib-slaac.h)


Does Doxygen resolve the file reference? If not, it would be good to add an explicit reference command.

crasbe · 2025-06-19T20:52:29Z

sys/net/gnrc/network_layer/ipv6/nib/_nib-slaac.h

+ * @param netif Network interface of the temporary address and the SLAAC prefix.
+ * @param addr Current temporary address (or any address in the SLAAC prefix for that matter)
+ * @param retries passed as-is to @ref _generate_temporary_addr
+ * @param caller_description Text detail for logging


These parameters are missing the direction.

crasbe · 2025-06-19T20:53:31Z

sys/net/gnrc/network_layer/ipv6/nib/nib.c

@@ -1539,6 +1559,31 @@ static void _handle_pfx_timeout(_nib_offl_entry_t *pfx)
                netif->ipv6.addrs_flags[i] |= GNRC_NETIF_IPV6_ADDRS_FLAGS_STATE_DEPRECATED;
            }
        }
+#if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES)
+        if (pfx->flags & _PFX_SLAAC) {
+            /* Remove regen event from temporary addresses (the current temporary address should have one scheduled).


This line causes a static error because it's too long.

crasbe · 2025-06-19T20:53:44Z

sys/net/gnrc/network_layer/ipv6/nib/nib.c

+             * because the temporary address is deprecated but not invalidated/removed yet.
+             */
+
+            //alternative way to get ta_pfx: _iter_slaac_prefix_to_temp_addr + _nib_offl_get_match


crasbe · 2025-06-19T20:53:58Z

sys/net/gnrc/network_layer/ipv6/nib/nib_pl.c

@@ -25,6 +25,9 @@

 #include "_nib-internal.h"
 #include "_nib-router.h"
+#if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES)
+#include "_nib-slaac.h"


Suggested change

#include "_nib-slaac.h"

# include "_nib-slaac.h"

crasbe · 2025-06-19T20:54:17Z

sys/shell/cmds/gnrc_netif.c

@@ -34,6 +34,9 @@
 #include "net/loramac.h"
 #include "net/netif.h"
 #include "shell.h"
+#if IS_ACTIVE(CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES)
+#include "../../net/gnrc/network_layer/ipv6/nib/_nib-slaac.h"


Suggested change

#include "../../net/gnrc/network_layer/ipv6/nib/_nib-slaac.h"

# include "../../net/gnrc/network_layer/ipv6/nib/_nib-slaac.h"

Again, I wonder why such sn explicit path is required.

xnumad requested review from leandrolanzieri, jia200x, MrKevinWeiss, miri64 and PeterKietzmann as code owners February 11, 2024 01:30

github-actions bot added Area: network Area: Networking Area: tests Area: tests and testing framework Area: sys Area: System Area: Kconfig Area: Kconfig integration labels Feb 11, 2024

This was referenced Feb 11, 2024

gnrc_ipv6_nib/SLAAC: rfc7217 stable privacy addresses #20370

Open

gnrc_ipv6_nib: Force unspecified next hop addresses #20371

Merged

xnumad force-pushed the rfc8981 branch from 0801f9a to 13dbe4e Compare June 19, 2024 07:57

xnumad force-pushed the rfc8981 branch 2 times, most recently from 5d5b8c6 to fa54557 Compare August 26, 2024 09:41

xnumad force-pushed the rfc8981 branch from fa54557 to fe10bfe Compare September 18, 2024 14:51

xnumad force-pushed the rfc8981 branch from b19fc15 to 8ae183f Compare September 18, 2024 14:53

xnumad force-pushed the rfc8981 branch from 8ae183f to 95b3b5c Compare September 20, 2024 06:02

xnumad force-pushed the rfc8981 branch from 95b3b5c to b4439c7 Compare October 17, 2024 19:32

xnumad added 8 commits June 19, 2025 01:45

includes

53aeeee

config: Define feature flag

ead2bc9

config: RFC params

ff8c8a4

Increase addr limit

46eed1c

SLAAC only for /64 prefixes

0da4ae4

config: RFC regen advance constant

781fab5

creation: Check IANA IID

8c92236

IDGEN

0dd9228

xnumad added 23 commits June 19, 2025 01:45

Documentation

8329cc2

6lowpan: Register temporary address

af2ba9b

Documentation: backlink

120b9ba

Document

20aae6c

fix compile on board

c14a748

gnrc_netif_ipv6_addr_pfx_idx

0cddaec

Supress SLAAC trigger also for 6lo

3d28b23

Need to check for matching address rather than prefix because for a 6LN, the SLAAC prefix is never stored in the prefix list, since everything is considered off-link.

Readability

06f688e

ifconfig: Print TMP property

0330f2b

Documentation

c2294b2

Adjust log levels

c2298e6

fixup! gnrc_netif_ipv6_addr_pfx_idx

0c2f141

fixup! gnrc_netif_ipv6_addr_pfx_idx

b182c49

fixup! creation: Add index param

454edae

fixup! config: RFC params

481c210

fixup! Handle DAD failure for temporary address

bfbb724

Log it

fixup! Temporary address creation

84219a3

Fix time units

docs: Wording

2b4874b

fix: Delete regen timer on deprecation

8389992

refactor: Move regen event from SLAAC prefix to ta_pfx

5ce2e2f

Increases readability Was previously also needed to enable regen to work on 6LN, because a 6LN did not store SLAAC prefix prior to PR RIOT-OS#20757.

refactor: Extract duplicate code to method

087dc9c

Adjust for PR RIOT-OS#20371

992147c

As the ta_pfx will have an NCE with unspecified next hop, 1 NCE is needed for that.

xnumad force-pushed the rfc8981 branch from b4439c7 to 992147c Compare June 18, 2025 23:50

crasbe added Type: new feature The issue requests / The PR implemements a new feature for RIOT CI: ready for build If set, CI server will compile all applications for all available boards for the labeled PR labels Jun 19, 2025

crasbe reviewed Jun 19, 2025

View reviewed changes

	#define GNRC_IPV6_NIB_REGEN_TEMP_ADDR (0x4fd6U)
	# define GNRC_IPV6_NIB_REGEN_TEMP_ADDR (0x4fd6U)

	#define CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES 0
	# define CONFIG_GNRC_IPV6_NIB_SLAAC_TEMPORARY_ADDRESSES 0

	#include "../../net/gnrc/network_layer/ipv6/nib/_nib-slaac.h"
	# include "../../net/gnrc/network_layer/ipv6/nib/_nib-slaac.h"

gnrc_ipv6_nib/SLAAC: rfc8981 temporary address (privacy extensions) #20369

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gnrc_ipv6_nib/SLAAC: rfc8981 temporary address (privacy extensions) #20369

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xnumad commented Feb 11, 2024 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Contribution description

Design

RFC compatibility

Adaptability

Testing procedure

Uh oh!

kaspar030 commented Feb 21, 2024

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xnumad commented Aug 26, 2024

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xnumad commented Sep 18, 2024

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xnumad commented Sep 18, 2024

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xnumad commented Jun 18, 2025

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crasbe commented Jun 19, 2025

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riot-ci commented Jun 19, 2025

Murdock results

Artifacts

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xnumad commented Feb 11, 2024 •

edited

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