RTNETLINK complaining about "No buffer space available" (also SIOCSIFADDR)
I'm writing this to save somebody a headache.
My router does IPv4 and IPv6, and has been doing so for a while. I started noticing that when connecting to my own server from my own home, it would take a while. I whittled it down to it trying to connect with IPv6 first, failing and then falling back to IPv4 which worked fine.
Now, why had my IPv6 died? To cut a long story short, here's why:
router # ip link show eth1
4: eth1: mtu 576 qdisc pfifo_fast state UP qlen 1000
link/ether 00:50:bf:21:b2:52 brd ff:ff:ff:ff:ff:ff
Look closely. Closer. The MTU is 576. No buffer space? Well, that just means the MTU is too low for IPv6! The error mesasge couldn't have been more clear! Err...
router # ip link set eth1 mtu 1500
BAM! Now it works again.
So why was the MTU set to 576? dhcpcd set it to that value! A-ha. Apparently this also happens to dhclient, and I guess the two are intertwined in some weird open-source way. My more persistent solution?
router # unlink /lib/dhcpcd/dhcpcd-hooks/10-mtu
BAM! Now it won't break for a while.
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