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Date: Sun, 21 Jan 2024 21:10:20 -0700
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Subject: Re: [Discuss]iproute2: ipv6 route add fail
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To: gaoxingwang <gaoxingwang1@huawei.com>, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
 kuba@kernel.org
Cc: liaichun@huawei.com, yanan@huawei.com
References: <20240105094255.1498461-1-gaoxingwang1@huawei.com>
From: David Ahern <dsahern@kernel.org>
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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`