Linux set min_rto on IPv6 device

user3870920 asked:

I came across http://unix.stackexchange.com/questions/210367/changing-the-tcp-rto-value-in-linux which pretty much does exactly what I want, but I need to do it with an IPv6 tunnel.

$ sudo ip -6 route
aaaa::/64 dev tun0  proto kernel  metric 256
fe80::/64 dev eth0  proto kernel  metric 256
fe80::/64 dev wlan0  proto kernel  metric 256
fe80::/64 dev tun0  proto kernel  metric 256

Then, if I look at my active connections we see:

$ ss -i
tcp   ESTAB      0      0                                                                                             aaaa::1:51692

         cubic rto:360 rtt:157.424/6.438 ato:40 mss:64 cwnd:10 send 32.5Kbps pacing_rate 65.0Kbps rcv_space:28800

It currently has an rto of 360. This device only deals withs super low bandwidth, high latency, lossy networks (i.e. 6LoWPaN) so I want to increase the min_rto to at least several seconds.

I have disabled frto:

$ sudo cat /proc/sys/net/ipv4/tcp_frto
0

Now I want to set min_rto, as shown in the linked question.

$ sudo ip -6 route change aaaa:: dev tun0 rto_min 2000
RTNETLINK answers: No such file or directory

Why do I get this error and how can I fix it?

It’s worth noting that if I do 2000ms (or 5ms, as in the linked answer), it tells me it’s an invalid value, hence why I dropped off the ms part. In case it matters, my Linux info is below:

Linux 4.4.13-v7+ #894 SMP Mon Jun 13 13:13:27 BST 2016 armv7l GNU/Linux

My answer:


The tcp_* settings listed under IPv4 also apply to IPv6, according to the documentation.

IPv6 has no global variables such as tcp_*.  tcp_* settings under ipv4/ also
apply to IPv6 [XXX?].

Given the question in the documentation there, it would be wise to verify this applies to your specific (older) kernel before proceeding.


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