netdev - Re: [Discuss]iproute2: ipv6 route add fail

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Message-ID: <90209854-8515-4f1e-8d6b-0182c8cab7ea@kernel.org>
Date: Sun, 21 Jan 2024 21:10:20 -0700
From: David Ahern <dsahern@...nel.org>
To: gaoxingwang <gaoxingwang1@...wei.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org
Cc: liaichun@...wei.com, yanan@...wei.com
Subject: Re: [Discuss]iproute2: ipv6 route add fail

On 1/5/24 2:42 AM, gaoxingwang wrote:
> Hello everyone,
> 
> Here is a particular problem with routing.
> Sometimes users can run the ip -6 route command to add a route whose destination address is the same as the gateway address, and it can be successfully added. However, adding another route with the same gateway address will fail later.
> 
> Example:
> # ip -6 route add 2409:8080:5a0a:60c7::7/128 via 2409:8080:5a0a:60c7::7 dev eth2
> # ip -6 route add 2409:8080:5a0a:60c7::8/128 via 2409:8080:5a0a:60c7::7 dev eth2
> RTNETLINK answers: No route to host
> 
> Does the kernel not support this application scenario?
> Or should the kernel not allow routes with the same destination address as the gateway address to be added so that other more meaningful routes can be added successfully?
> 
> This question puzzles me, thank you very much if your can reply.

try running `perf record -e fib6:*` and then run both route commands
above. After both have run, Ctrl-C on perf and then run `perf script`