Eric, I don't know if that's a good test case but on my patched Trusty box:
root@xeon:~# uname -a
Linux xeon 3.13.0-63-generic #103-Ubuntu SMP Fri Aug 14 21:42:59 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
root@xeon:~# sysctl net.core.wmem_max=4650
net.core.wmem_max = 4700
root@xeon:~# sysctl net.core.rmem_max=2400
net.core.rmem_max = 2400
root@xeon:~# (ip -4 ro ; ip -6 ro) | wc -l
43
root@xeon:~# (ip -4 a; ip -6 a) | grep -c inet
34
root@xeon:~# ip link | grep -c link
23
root@xeon:~# dpkg -l | awk '{if ($2 == "ntp") print $3}'
1:4.2.6.p5+dfsg-3ubuntu2.14.04.4
root@xeon:~# /etc/init.d/ntp restart
root@xeon:~# netstat -puant | grep -c ntpd
36
Then syslog shows nothing abnormal. It says "Listen normally on {2..35}". FYI, many of those interfaces a vnetX interfaces belonging to VMs so I don't know if they really count. Trying to lower {r,w}mem_max even more result in "Invalid argument". Please let me know if I'm doing something wrong.
Eric, I don't know if that's a good test case but on my patched Trusty box:
root@xeon:~# uname -a wmem_max= 4650 rmem_max= 2400 6.p5+dfsg- 3ubuntu2. 14.04.4
Linux xeon 3.13.0-63-generic #103-Ubuntu SMP Fri Aug 14 21:42:59 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
root@xeon:~# sysctl net.core.
net.core.wmem_max = 4700
root@xeon:~# sysctl net.core.
net.core.rmem_max = 2400
root@xeon:~# (ip -4 ro ; ip -6 ro) | wc -l
43
root@xeon:~# (ip -4 a; ip -6 a) | grep -c inet
34
root@xeon:~# ip link | grep -c link
23
root@xeon:~# dpkg -l | awk '{if ($2 == "ntp") print $3}'
1:4.2.
root@xeon:~# /etc/init.d/ntp restart
root@xeon:~# netstat -puant | grep -c ntpd
36
Then syslog shows nothing abnormal. It says "Listen normally on {2..35}". FYI, many of those interfaces a vnetX interfaces belonging to VMs so I don't know if they really count. Trying to lower {r,w}mem_max even more result in "Invalid argument". Please let me know if I'm doing something wrong.