Grzegorz Junka wrote on 05/18/2016 18:37:
What may be the reason that netstat -rn works in one jail and doesn't in
another?

root@app2:/ # netstat -rn
Routing tables

Internet:
Destination        Gateway            Flags      Netif Expire
192.168.1.76       link#4             UHS         lo0


root@pjp1:/ # netstat -rn
netstat: kvm not available: /dev/mem: No such file or directory
Routing tables
rt_tables: symbol not in namelist

I don't know the reason but I can confirm this behavior. I know about this for a long time. Netstat complains about /dev/mem for some other params too even if it outputs correct values for example for opened tcp connections:

/# netstat -s -p tcp
netstat: kvm not available: /dev/mem: No such file or directory
tcp:
        1517892073 packets sent
                1453939900 data packets (2274781047202 bytes)
                759536 data packets (929141944 bytes) retransmitted
                59175 data packets unnecessarily retransmitted
                0 resends initiated by MTU discovery
                51907865 ack-only packets (26667901 delayed)
                0 URG only packets
                267 window probe packets
                795506 window update packets
                10493883 control packets
        1487401217 packets received
                1417951529 acks (for 2273802396874 bytes)
                7502860 duplicate acks
                38600 acks for unsent data
1368386110 packets (2153255668968 bytes) received in-sequence
                222423 completely duplicate packets (39239815 bytes)
                11980 old duplicate packets
                221 packets with some dup. data (94160 bytes duped)
                35171 out-of-order packets (15770219 bytes)
                21 packets (11 bytes) of data after window
                11 window probes
                1863690 window update packets
                1642030 packets received after close
                281 discarded for bad checksums
                0 discarded for bad header offset fields
                0 discarded because packet too short
                87 discarded due to memory problems
        2448384 connection requests
        7800552 connection accepts
        0 bad connection attempts
        109 listen queue overflows
        339306 ignored RSTs in the windows
        10221160 connections established (including accepts)
        10554092 connections closed (including 1990441 drops)
                5674590 connections updated cached RTT on close
                5677848 connections updated cached RTT variance on close
                1583021 connections updated cached ssthresh on close
        10125 embryonic connections dropped
        1405786035 segments updated rtt (of 1374995187 attempts)
        404689 retransmit timeouts
                1681 connections dropped by rexmit timeout
        608 persist timeouts
                0 connections dropped by persist timeout
        0 Connections (fin_wait_2) dropped because of timeout
        12388 keepalive timeouts
                11896 keepalive probes sent
                492 connections dropped by keepalive
        38184853 correct ACK header predictions
        46419366 correct data packet header predictions
        7826351 syncache entries added
                45759 retransmitted
                55797 dupsyn
                84 dropped
                7800552 completed
                40 bucket overflow
                0 cache overflow
                19220 reset
                7941 stale
                109 aborted
                0 badack
                230 unreach
                0 zone failures
        7826435 cookies sent
        1784 cookies received
        212203 hostcache entries added
                28 bucket overflow
        104273 SACK recovery episodes
        242234 segment rexmits in SACK recovery episodes
        303575028 byte rexmits in SACK recovery episodes
        1538523 SACK options (SACK blocks) received
        12421 SACK options (SACK blocks) sent
        114 SACK scoreboard overflow
        0 packets with ECN CE bit set
        0 packets with ECN ECT(0) bit set
        0 packets with ECN ECT(1) bit set
        0 successful ECN handshakes
        0 times ECN reduced the congestion window
        0 packets with valid tcp-md5 signature received
        0 packets with invalid tcp-md5 signature received
        0 packets with tcp-md5 signature mismatch
        0 packets with unexpected tcp-md5 signature received
        0 packets without expected tcp-md5 signature received


I tried netstat -rn in all 8 jails on our test machine. 4 of them works, the other 4 don't work.

netstat -rn doesn't work in those jail which are older than host environment

netstat -s -p tcp prints error message even in the newest jails:
netstat: kvm not available: /dev/mem: No such file or directory


Miroslav Lachman

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