gnrc_ipv6_nib: don't auto-configure IPv6 w/o SLAAC on non-6LN interface #12513

miri64 · 2019-10-20T14:26:06Z

Contribution description

When the NIB is compiled for 6LN mode (but not a 6LBR), the Stateless Address Autoconfiguration (SLAAC) functionality is disabled, as it is typically not required; see

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

Lines 41 to 48 in d9c240a

    
           #ifdef MODULE_GNRC_IPV6_NIB_6LR 
        
           #ifndef GNRC_IPV6_NIB_CONF_6LR 
        
           #define GNRC_IPV6_NIB_CONF_6LR          (1) 
        
           #endif 
        
           #ifndef GNRC_IPV6_NIB_CONF_SLAAC 
        
           #define GNRC_IPV6_NIB_CONF_SLAAC        (0) 
        
           #endif 
        
           #endif

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

Lines 50 to 59 in d9c240a

    
           #ifdef MODULE_GNRC_IPV6_NIB_6LN 
        
           #ifndef GNRC_IPV6_NIB_CONF_6LN 
        
           #define GNRC_IPV6_NIB_CONF_6LN          (1) 
        
           #endif 
        
           #ifndef GNRC_IPV6_NIB_CONF_SLAAC 
        
           #define GNRC_IPV6_NIB_CONF_SLAAC        (0) 
        
           #endif 
        
           #ifndef GNRC_IPV6_NIB_CONF_QUEUE_PKT 
        
           #define GNRC_IPV6_NIB_CONF_QUEUE_PKT    (0) 
        
           #endif

However, if a non-6LN interface is also compiled in (still without making the node a border router) an auto-configured address will be assigned in accordance with RFC 6775 to the interface, just assuming the interface is a 6LN interface. As it then only performs duplicate address detection RFC-6775-style then, the address then never becomes valid, as the duplicate address detection according to RFC 4862 (part of the SLAAC functionality) is never performed.

As auto-configuring an address without SLAAC doesn't make sense, this fix makes the interface skip it completely, but provides a warning to the user, so they know what to do.

Testing procedure

Compile examples/gnrc_networking native with both a netdev_tap and socket_zep:

GNRC_NETIF_NUMOF=2 USEMODULE=socket_zep TERMFLAGS="-z [::]:17755 tap0" \
   make -C examples/gnrc_networking all term

With this fix, the link-local address of the Ethernet interface won't receive an auto-configured link-local address and a warning is printed

RIOT native interrupts/signals initialized.
LED_RED_OFF
LED_GREEN_ON
RIOT native board initialized.
RIOT native hardware initialization complete.

SLAAC not activated; won't auto-configure IPv6 for interface 7
    Use GNRC_IPV6_NIB_CONF_SLAAC=1 to activate
main(): This is RIOT! (Version: 2020.01-devel-197-gc93b3-gnrc_netif/enh/split-6lo-6ln)
RIOT network stack example application
All up, running the shell now
> ifconfig
ifconfig
Iface  7  HWaddr: 26:82:DC:3B:CA:E6 
          L2-PDU:1500 MTU:1500  HL:64  RTR  
          Source address length: 6
          Link type: wired
          inet6 group: ff02::2
          inet6 group: ff02::1
          
          Statistics for Layer 2
            RX packets 4  bytes 440
            TX packets 3 (Multicast: 3)  bytes 186
            TX succeeded 3 errors 0
          Statistics for IPv6
            RX packets 4  bytes 384
            TX packets 3 (Multicast: 3)  bytes 144
            TX succeeded 3 errors 0

Iface  8  HWaddr: 45:5B  Channel: 26  NID: 0x23
          Long HWaddr: 00:5A:45:50:0A:00:45:5B 
          L2-PDU:102 MTU:1280  HL:64  RTR  
          6LO  IPHC  
          Source address length: 8
          Link type: wireless
          inet6 addr: fe80::25a:4550:a00:455b  scope: local  VAL
          inet6 group: ff02::2
          inet6 group: ff02::1
          inet6 group: ff02::1:ff00:455b
          
          Statistics for Layer 2
            RX packets 0  bytes 0
            TX packets 3 (Multicast: 3)  bytes 86
            TX succeeded 6 errors 0
          Statistics for IPv6
            RX packets 0  bytes 0
            TX packets 3 (Multicast: 3)  bytes 192
            TX succeeded 3 errors 0

Compiling with CFLAGS+=-DGNRC_IPV6_NIB_CONF_SLAAC=1 still auto-configures the address and validates it shortly after the node started (and the warning is not shown ;-)):

> ifconfig
ifconfig
Iface  7  HWaddr: 26:82:DC:3B:CA:E6 
          L2-PDU:1500 MTU:1500  HL:64  RTR  
          Source address length: 6
          Link type: wired
          inet6 addr: fe80::2482:dcff:fe3b:cae6  scope: local  VAL
          inet6 group: ff02::2
          inet6 group: ff02::1
          inet6 group: ff02::1:ff3b:cae6
          
          Statistics for Layer 2
            RX packets 5  bytes 526
            TX packets 2 (Multicast: 2)  bytes 140
            TX succeeded 2 errors 0
          Statistics for IPv6
            RX packets 5  bytes 456
            TX packets 2 (Multicast: 2)  bytes 112
            TX succeeded 2 errors 0

Iface  8  HWaddr: 45:5B  Channel: 26  NID: 0x23
          Long HWaddr: 00:5A:45:50:0A:00:45:5B 
          L2-PDU:102 MTU:1280  HL:64  RTR  
          6LO  IPHC  
          Source address length: 8
          Link type: wireless
          inet6 addr: fe80::25a:4550:a00:455b  scope: local  VAL
          inet6 group: ff02::2
          inet6 group: ff02::1
          inet6 group: ff02::1:ff00:455b
          
          Statistics for Layer 2
            RX packets 0  bytes 0
            TX packets 2 (Multicast: 2)  bytes 43
            TX succeeded 3 errors 0
          Statistics for IPv6
            RX packets 0  bytes 0
            TX packets 2 (Multicast: 2)  bytes 128
            TX succeeded 2 errors 0

Without the fix and CFLAGS=-DGNRC_IPV6_NIB_CONF_SLAAC=1 not set the Ethernet interface gets a link-local address which will stay tentative forever:

> ifconfig
ifconfig
Iface  7  HWaddr: 26:82:DC:3B:CA:E6 
          L2-PDU:1500 MTU:1500  HL:64  RTR  
          Source address length: 6
          Link type: wired
          inet6 addr: fe80::2482:dcff:fe3b:cae6  scope: local  TNT[1]
          inet6 group: ff02::2
          inet6 group: ff02::1
          inet6 group: ff02::1:ff3b:cae6
          
          Statistics for Layer 2
            RX packets 5  bytes 526
            TX packets 1 (Multicast: 1)  bytes 62
            TX succeeded 1 errors 0
          Statistics for IPv6
            RX packets 5  bytes 456
            TX packets 1 (Multicast: 1)  bytes 48
            TX succeeded 1 errors 0

Iface  8  HWaddr: 45:5B  Channel: 26  NID: 0x23
          Long HWaddr: 00:5A:45:50:0A:00:45:5B 
          L2-PDU:102 MTU:1280  HL:64  RTR  
          6LO  IPHC  
          Source address length: 8
          Link type: wireless
          inet6 addr: fe80::25a:4550:a00:455b  scope: local  VAL
          inet6 group: ff02::2
          inet6 group: ff02::1
          inet6 group: ff02::1:ff00:455b
          
          Statistics for Layer 2
            RX packets 0  bytes 0
            TX packets 2 (Multicast: 2)  bytes 43
            TX succeeded 3 errors 0
          Statistics for IPv6
            RX packets 0  bytes 0
            TX packets 2 (Multicast: 2)  bytes 128
            TX succeeded 2 errors 0

Issues/PRs references

Several, but triggered by testing procedures in #12512 and #10499.

miri64 · 2019-10-20T14:27:21Z

@kb2ma this bug isn't really critical, as it only appears in very special configuration, so if it isn't in by RC2 when you create it, we shouldn't worry about that.

cgundogan · 2019-10-20T14:54:30Z

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

+    if (!gnrc_netif_is_6ln(netif)) {
+        LOG_WARNING("SLAAC not activated; won't auto-configure IPv6 for "
+                         "interface %u\n"
+                    "    Use " NAME(GNRC_IPV6_NIB_CONF_SLAAC) "=1 to "


Why wouldn't a simple

" Use GNRC_IPV6_NIB_CONF_SLAAC=1 to "

suffice? The stringification of a macro to print the macro name seems unnecessarily complex in this situation. Or are there other intentions (for future use)?

My main motivation is future-proofness, e.g. if the name of the macro changes. The example will cause an immediate compile-time error while just having a string literal won't.

The example will cause an immediate compile-time error while just having a string literal won't.

Did you test that? I also thought so and did a quick test using a puts(). I was able to put anything in NAME() without the compiler throwing an error.

No, I didn't I assumed the preprocessor checks what it is provided with. Ok then I do it the simple way ;-).

miri64 · 2019-10-20T15:44:21Z

Also fixed the wording to a less colloquial style.

cgundogan · 2019-10-20T16:20:51Z

Alright, the change seems sensible. Still needs a test, though. I will roll up my sleeves in a couple of hours, if nobody tested & confirmed the desired behaviour by then.

miri64 · 2019-10-20T20:46:30Z

Alright, the change seems sensible. Still needs a test, though. I will roll up my sleeves in a couple of hours, if nobody tested & confirmed the desired behaviour by then.

Don't you trust my results posted above? ^^

cgundogan · 2019-10-20T22:07:42Z

Don't you trust my results posted above? ^^

Sure. But you know: the devil is in the detail (: It doesn't hurt to verify your results .. and I just did 👍 looks good.

cgundogan

Please squash.

When the NIB is compiled for 6LN mode (but not a 6LBR), the Stateless Address Autoconfiguration (SLAAC) functionality is disabled, as it is typically not required; see `sys/include/net/gnrc/ipv6/nib/conf.h`, ll. 46 and 55. However, if a non-6LN interface is also compiled in (still without making the node a border router) an auto-configured address will be assigned in accordance with [RFC 6775] to the interface, just assuming the interface is a 6LN interface. As it then only performs duplicate address detection RFC-6775-style then, the address then never becomes valid, as the duplicate address detection according to [RFC 4862] (part of the SLAAC functionality) is never performed. As auto-configuring an address without SLAAC doesn't make sense, this fix makes the interface skip it completely, but provides a warning to the user, so they know what to do. [RFC 6775]: https://tools.ietf.org/html/rfc6775#section-5.2 [RFC 4862]: https://tools.ietf.org/html/rfc4862#section-5.4

cgundogan · 2019-10-20T23:01:39Z

Okay, Murdock shows finally green!

miri64 · 2019-10-21T07:25:52Z

Thanks for the review :-)

miri64 · 2019-10-21T07:46:00Z

Backport provided in #12522

Similar as with RIOT-OS#12513, when the NIB is compiled in 6LN mode (but not 6LR mode), the address-resolution state-machine (ARSM) functionality is disabled in favor of the more simpler address resolution proposed in RFC 6775. However, if a non-6LN interface is also compiled in (without making it a router or border router) it will never join the solicited-nodes multicast address of addresses added to it, resulting in address resolution to that interface to fail. If the interface is not a 6LN (which in case 6LN mode is disabled is always false), a warning is now printed, encouraging the user to activate the ARSM functionality if needed.

miri64 added this to the Release 2019.10 milestone Oct 20, 2019

miri64 requested review from benpicco and kb2ma October 20, 2019 14:26

miri64 mentioned this pull request Oct 20, 2019

gnrc_netif: introduce distinction if an interface supports 6Lo or if it performs ND according to RFC 6775 #10499

Merged

5 tasks

cgundogan reviewed Oct 20, 2019

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cgundogan added Reviewed: 1-fundamentals The fundamentals of the PR were reviewed according to the maintainer guidelines Reviewed: 2-code-design The code design of the PR was reviewed according to the maintainer guidelines labels Oct 20, 2019

cgundogan added the Reviewed: 4-code-style The adherence to coding conventions by the PR were reviewed according to the maintainer guidelines label Oct 20, 2019

cgundogan approved these changes Oct 20, 2019

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cgundogan added Reviewed: 3-testing The PR was tested according to the maintainer guidelines Reviewed: 5-documentation The documentation details of the PR were reviewed according to the maintainer guidelines labels Oct 20, 2019

miri64 force-pushed the gnrc_ipv6_fix/fix/auto-config-with-no-slaac-but-6ln branch from 35ebfbd to 7cba2fb Compare October 20, 2019 22:17

cgundogan merged commit e66283f into RIOT-OS:master Oct 20, 2019

miri64 deleted the gnrc_ipv6_fix/fix/auto-config-with-no-slaac-but-6ln branch October 21, 2019 07:25

miri64 mentioned this pull request Oct 21, 2019

gnrc_ipv6_nib: don't auto-configure IPv6 w/o SLAAC on non-6LN interface [backport 2019.10] #12522

Merged

chrysn mentioned this pull request Oct 22, 2019

No answers to Neighbor Solicitation when 6lo and non-6lo interfaces are mixed #12545

Closed

miri64 mentioned this pull request Oct 22, 2019

gnrc_netif: warn when not joining solicited-nodes from non-6LN netif #12547

Merged

miri64 restored the gnrc_ipv6_fix/fix/auto-config-with-no-slaac-but-6ln branch October 31, 2019 18:50

miri64 deleted the gnrc_ipv6_fix/fix/auto-config-with-no-slaac-but-6ln branch October 31, 2019 18:51

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gnrc_ipv6_nib: don't auto-configure IPv6 w/o SLAAC on non-6LN interface #12513

gnrc_ipv6_nib: don't auto-configure IPv6 w/o SLAAC on non-6LN interface #12513

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	#ifdef MODULE_GNRC_IPV6_NIB_6LR
	#ifndef GNRC_IPV6_NIB_CONF_6LR
	#define GNRC_IPV6_NIB_CONF_6LR (1)
	#endif
	#ifndef GNRC_IPV6_NIB_CONF_SLAAC
	#define GNRC_IPV6_NIB_CONF_SLAAC (0)
	#endif
	#endif

	#ifdef MODULE_GNRC_IPV6_NIB_6LN
	#ifndef GNRC_IPV6_NIB_CONF_6LN
	#define GNRC_IPV6_NIB_CONF_6LN (1)
	#endif
	#ifndef GNRC_IPV6_NIB_CONF_SLAAC
	#define GNRC_IPV6_NIB_CONF_SLAAC (0)
	#endif
	#ifndef GNRC_IPV6_NIB_CONF_QUEUE_PKT
	#define GNRC_IPV6_NIB_CONF_QUEUE_PKT (0)
	#endif

gnrc_ipv6_nib: don't auto-configure IPv6 w/o SLAAC on non-6LN interface #12513

gnrc_ipv6_nib: don't auto-configure IPv6 w/o SLAAC on non-6LN interface #12513

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Contribution description

Testing procedure

Issues/PRs references

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