Fix inifinte loop in esp32 RIO handling.

[cecille]

Problem

If the router is advertising a default prefix (::/0), the route
handler is going into an infinite loop.

Route information options can only have one prefix anyway, so the
loop here is overkill and likely to introduce bad routes.

Change overview

Change for loop to a simple check that the size is sufficient.

Testing

Configured radvd to advertise a default route, saw infinite loop on upstream, no problems with this code. Regular routes are being processed correctly.

[github-actions]

PR #12736: Size comparison from 1f4024a to 84dda1e

Decreases (2 builds for esp32)

platform	target	config	section	1f4024a	84dda1e	change	% change
esp32	all-clusters-app	c3devkit	(read only)	855952	855942	-10	-0.0
			.flash.text	855952	855942	-10	-0.0
		m5stack	(read only)	958923	958891	-32	-0.0
			.flash.text	953539	953507	-32	-0.0

Full report (32 builds for efr32, esp32, k32w, linux, mbed, nrfconnect, p6, qpg, telink)

platform	target	config	section	1f4024a	84dda1e	change	% change
efr32	lighting-app	BRD4161A	(read only)	794956	794956	0	0.0
			(read/write)	122996	122996	0	0.0
			.bss	121176	121176	0	0.0
			.data	1820	1820	0	0.0
			.text	794948	794948	0	0.0
		BRD4161A+rpc	(read only)	782552	782552	0	0.0
			(read/write)	139680	139680	0	0.0
			.bss	137752	137752	0	0.0
			.data	1928	1928	0	0.0
			.text	782544	782544	0	0.0
	window-app	BRD4161A	(read only)	771908	771908	0	0.0
			(read/write)	121136	121136	0	0.0
			.bss	119352	119352	0	0.0
			.data	1784	1784	0	0.0
			.text	771900	771900	0	0.0
esp32	all-clusters-app	c3devkit	(read only)	855952	855942	-10	-0.0
			(read/write)	1306034	1306034	0	0.0
			.dram0.bss	67648	67648	0	0.0
			.dram0.data	14124	14124	0	0.0
			.flash.rodata	171232	171232	0	0.0
			.flash.text	855952	855942	-10	-0.0
			.iram0.text	62076	62076	0	0.0
		m5stack	(read only)	958923	958891	-32	-0.0
			(read/write)	450252	450252	0	0.0
			.dram0.bss	75000	75000	0	0.0
			.dram0.data	34048	34048	0	0.0
			.flash.rodata	209416	209416	0	0.0
			.flash.text	953539	953507	-32	-0.0
			.iram0.text	123451	123451	0	0.0
k32w	lighting-app	k32w061+se05x+release	(read/write)	732132	732132	0	0.0
			.bss	81248	81248	0	0.0
			.data	1852	1852	0	0.0
			.text	643232	643232	0	0.0
	lock-app	k32w061+debug	(read/write)	622716	622716	0	0.0
			.bss	71912	71912	0	0.0
			.data	1820	1820	0	0.0
			.text	543184	543184	0	0.0
	shell	k32w061+debug	(read/write)	685808	685808	0	0.0
			.bss	81612	81612	0	0.0
			.data	1792	1792	0	0.0
			.text	596604	596604	0	0.0
linux	chip-tool-ipv6only	arm64	(read only)	6665652	6665652	0	0.0
			(read/write)	305217	305217	0	0.0
			.bss	51665	51665	0	0.0
			.data	1048	1048	0	0.0
			.data.rel.ro	201888	201888	0	0.0
			.dynamic	560	560	0	0.0
			.got	46984	46984	0	0.0
			.init	24	24	0	0.0
			.init_array	160	160	0	0.0
			.rodata	338548	338548	0	0.0
			.text	5682820	5682820	0	0.0
	thermostat-no-ble	arm64	(read only)	1906556	1906556	0	0.0
			(read/write)	135825	135825	0	0.0
			.bss	59457	59457	0	0.0
			.data	776	776	0	0.0
			.data.rel.ro	69280	69280	0	0.0
			.dynamic	560	560	0	0.0
			.got	3456	3456	0	0.0
			.init	24	24	0	0.0
			.init_array	256	256	0	0.0
			.rodata	123964	123964	0	0.0
			.text	1577744	1577744	0	0.0
mbed	all-clusters-app	CY8CPROTO_062_4343W+release	(read only)	6224	6224	0	0.0
			(read/write)	2316496	2316496	0	0.0
			.bss	186900	186900	0	0.0
			.data	5232	5232	0	0.0
			.heap	844312	844312	0	0.0
			.text	1279072	1279072	0	0.0
	lighting-app	CY8CPROTO_062_4343W+release	(read only)	6224	6224	0	0.0
			(read/write)	2299016	2299016	0	0.0
			.bss	175712	175712	0	0.0
			.data	5488	5488	0	0.0
			.heap	855248	855248	0	0.0
			.text	1261616	1261616	0	0.0
	lock-app	CY8CPROTO_062_4343W+release	(read only)	6224	6224	0	0.0
			(read/write)	2271928	2271928	0	0.0
			.bss	174752	174752	0	0.0
			.data	5488	5488	0	0.0
			.heap	856208	856208	0	0.0
			.text	1234528	1234528	0	0.0
	pigweed-app	CY8CPROTO_062_4343W+release	(read only)	6224	6224	0	0.0
			(read/write)	1140008	1140008	0	0.0
			.bss	11756	11756	0	0.0
			.data	4376	4376	0	0.0
			.heap	1020312	1020312	0	0.0
			.text	103392	103392	0	0.0
	shell	CY8CPROTO_062_4343W+release	(read only)	6224	6224	0	0.0
			(read/write)	2047808	2047808	0	0.0
			.bss	156564	156564	0	0.0
			.data	4864	4864	0	0.0
			.heap	875016	875016	0	0.0
			.text	1010408	1010408	0	0.0
nrfconnect	lighting-app	nrf52840dk_nrf52840	(read/write)	897027	897027	0	0.0
			bss	116184	116184	0	0.0
			rodata	100172	100172	0	0.0
			text	605116	605116	0	0.0
		nrf52840dk_nrf52840+rpc	(read/write)	860051	860051	0	0.0
			bss	112532	112532	0	0.0
			rodata	91468	91468	0	0.0
			text	579844	579844	0	0.0
		nrf5340dk_nrf5340_cpuapp	(read/write)	822974	822974	0	0.0
			bss	117560	117560	0	0.0
			rodata	95432	95432	0	0.0
			text	535496	535496	0	0.0
	lock-app	nrf52840dk_nrf52840	(read/write)	869499	869499	0	0.0
			bss	113448	113448	0	0.0
			rodata	96292	96292	0	0.0
			text	584376	584376	0	0.0
		nrf5340dk_nrf5340_cpuapp	(read/write)	795698	795698	0	0.0
			bss	114856	114856	0	0.0
			rodata	91580	91580	0	0.0
			text	514848	514848	0	0.0
	pigweed-app	nrf52840dk_nrf52840	(read/write)	497463	497463	0	0.0
			bss	51820	51820	0	0.0
			rodata	45852	45852	0	0.0
			text	339492	339492	0	0.0
	pump-app	nrf52840dk_nrf52840	(read/write)	874347	874347	0	0.0
			bss	113360	113360	0	0.0
			rodata	97644	97644	0	0.0
			text	587892	587892	0	0.0
	pump-controller-app	nrf52840dk_nrf52840	(read/write)	867587	867587	0	0.0
			bss	113236	113236	0	0.0
			rodata	95780	95780	0	0.0
			text	583112	583112	0	0.0
	shell	nrf52840dk_nrf52840	(read/write)	781611	781611	0	0.0
			bss	109552	109552	0	0.0
			rodata	74280	74280	0	0.0
			text	523264	523264	0	0.0
		nrf5340dk_nrf5340_cpuapp	(read/write)	696686	696686	0	0.0
			bss	110532	110532	0	0.0
			rodata	68920	68920	0	0.0
			text	443904	443904	0	0.0
p6	all-clusters-app	default	(read/write)	2350400	2350400	0	0.0
			.bss	113132	113132	0	0.0
			.data	2512	2512	0	0.0
			.heap	917696	917696	0	0.0
			.text	1308664	1308664	0	0.0
	light-app	default	(read/write)	2281464	2281464	0	0.0
			.bss	100904	100904	0	0.0
			.data	2328	2328	0	0.0
			.heap	930112	930112	0	0.0
			.text	1239728	1239728	0	0.0
	lock-app	default	(read/write)	2257568	2257568	0	0.0
			.bss	99784	99784	0	0.0
			.data	2288	2288	0	0.0
			.heap	931272	931272	0	0.0
			.text	1215832	1215832	0	0.0
qpg	lighting-app	qpg6100+debug	(read only)	511948	511948	0	0.0
			(read/write)	122332	122332	0	0.0
			.bss	82624	82624	0	0.0
			.data	956	956	0	0.0
			.text	506628	506628	0	0.0
	lock-app	qpg6100+debug	(read only)	486140	486140	0	0.0
			(read/write)	122336	122336	0	0.0
			.bss	81760	81760	0	0.0
			.data	912	912	0	0.0
			.text	480820	480820	0	0.0
	persistent-storage-app	qpg6100+debug	(read only)	108104	108104	0	0.0
			(read/write)	122336	122336	0	0.0
			.bss	36152	36152	0	0.0
			.data	288	288	0	0.0
			.text	102784	102784	0	0.0
telink	lighting-app	tlsr9518adk80d	(read/write)	800386	800386	0	0.0
			bss	82764	82764	0	0.0
			noinit	37160	37160	0	0.0
			text	557446	557446	0	0.0

[andy31415]

Fast track due to small size.

This is more of a hotfix: this was demostratably causing infinite loops and that was fixed and tested. Any followup reviews will be done separately. For now, pushing the 'stop the ability to busyloop' out of the way.

[gjc13]

It's fine to just use if (rio_data_len >= prefix_len_bytes) to check for the prefix data since there will only be on prefix in each RIO record.