Date: Thu, 02 Jul 2020 17:24:55 +0000 From: bugzilla-noreply@freebsd.org To: net@FreeBSD.org Subject: [Bug 247700] rtadvd: fails to generate error when iface lacks a link-local address Message-ID: <bug-247700-7501-DEx5GU80jk@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-247700-7501@https.bugs.freebsd.org/bugzilla/> References: <bug-247700-7501@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=247700 --- Comment #3 from Hiroki Sato <hrs@FreeBSD.org> --- It is a valid situation for a unicast communication where a global-scope address is the source address and a link-local-scope address is the destination address though it is not recognized as valid as a Router Advertisement message. Limiting the address selection to the same zone as the destination's is too restrictive. The current implementation prefers a source scope whose scope is larger than the destination's (c.f. Rule 2, Sec. 5, RFC 6724). Even if the source is smaller than the destination, an address is selected in any way. However, upon sending a packet, the network stack will discard the packet due to an error "no destination". So in the situation with src=GUA/dst=LLA, a unicast communication works and it does not against the specifications. Usually it does not happen because every interface has at least one LLA configured (c.f. Sec. 2.1, RFC 4291) and the source address selection algorithm always prefers a smaller scope. For an interface with no LLA, I think NDP does not work in various ways because it (and MLDv2) heavily depends on LLA. It is not limited to Router Advertisement messages. For this reason, FreeBSD configures an EUI-64 LLA by default. There are some scenarios where only GUAs are configured on an interface, however. To prevent rtadvd(8) from sending invalid packets you reported, I think rtadvd(8) should check if the interface has an LLA or not. I believe running rtadvd(8) on an interface with no LLA is a wrong configuration. Please let me know if I understand your report correctly, and comments about my understanding about the issue you pointed out. If the additional check on rtadvd(8) is sufficient, I will work on it. -- You are receiving this mail because: You are on the CC list for the bug.
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