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Re: Strange TCP problem with awge0
On Fri, Jan 02, 2015 at 10:17:01AM -0800, Dennis Ferguson wrote:
> It looks to me like the packet that isn't being ack'd may actually be
> going in the other direction, from the server to the client. It is
> always this one, the same in every trace:
>
> 06:30:36.457041 IP (tos 0x0, ttl 50, id 27541, offset 0, flags [DF], proto TCP (6), length 61)
> ftp.solnet.ch.ftp > ip-176-199-201-17.hsi06.unitymediagroup.de.65151: Flags [P.], cksum 0xe404 (correct), seq 1296:1305, ack 43, win 1040, options [nop,nop,TS val 3171079293 ecr 1], length 9
> 0x0000: 4500 003d 6b95 4000 3206 89f3 d465 04f4 E..=k.@.2....e..
> 0x0010: b0c7 c911 0015 fe7f e09e abf3 1996 ee58 ...............X
> 0x0020: 8018 0410 e404 0000 0101 080a bd02 d47d ...............}
> 0x0030: 0000 0001 3231 3120 456e 640d 0a ....211.End..
Ok, I see this packet show up in a tcpdump on the awge interface, so
should be able to trace it further. This is (currently) all software
checksums, and since the packet made it to the bpf_mtap, it can't be
hardware. I don't see an ACK to this packet in the local trace, so I guess
it realy is the receiving side somewhere further up in the stack that
drops it.
netstat -s below...
I wonder where the PMTUD blackhole comes from (MTU on awge is 1500,
just like on the other machines here that can do the test without
adding a PMTUD blackhole).
Martin
icmp:
0 calls to icmp_error
0 errors not generated because old message was icmp
Output histogram:
echoreply: 1
0 messages with bad code fields
0 messages < minimum length
0 bad checksums
0 messages with bad length
0 multicast echo requests ignored
0 multicast timestamp requests ignored
Input histogram:
echo: 1
photuris: 1096454688104512
1 message response generated
0 path MTU changes
igmp:
1 message received
0 messages received with too few bytes
0 messages received with bad checksum
1 membership query received
0 membership queries received with invalid field(s)
0 membership reports received
0 membership reports received with invalid field(s)
0 membership reports received for groups to which we belong
0 membership reports sent
tcp:
250 packets sent
170 data packets (33646 bytes)
0 data packets (0 bytes) retransmitted
70 ack-only packets (197 delayed)
0 URG only packets
0 window probe packets
1 window update packet
9 control packets
0 send attempts resulted in self-quench
284 packets received
163 acks (for 33649 bytes)
1 duplicate ack
0 acks for unsent data
250 packets (29579 bytes) received in-sequence
0 completely duplicate packets (0 bytes)
0 old duplicate packets
0 packets with some dup. data (0 bytes duped)
0 out-of-order packets (0 bytes)
0 packets (0 bytes) of data after window
0 window probes
2 window update packets
0 packets received after close
9 discarded for bad checksums
0 discarded for bad header offset fields
0 discarded because packet too short
2 connection requests
2 connection accepts
4 connections established (including accepts)
7 connections closed (including 0 drops)
0 embryonic connections dropped
0 delayed frees of tcpcb
165 segments updated rtt (of 161 attempts)
5 retransmit timeouts
0 connections dropped by rexmit timeout
0 persist timeouts (resulting in 0 dropped connections)
0 keepalive timeouts
0 keepalive probes sent
0 connections dropped by keepalive
0 correct ACK header predictions
100 correct data packet header predictions
4 PCB hash misses
0 dropped due to no socket
0 connections drained due to memory shortage
1 PMTUD blackhole detected
0 bad connection attempts
2 SYN cache entries added
0 hash collisions
2 completed
0 aborted (no space to build PCB)
0 timed out
0 dropped due to overflow
0 dropped due to bucket overflow
0 dropped due to RST
0 dropped due to ICMP unreachable
2 delayed free of SYN cache entries
0 SYN,ACKs retransmitted
0 duplicate SYNs received for entries already in the cache
0 SYNs dropped (no route or no space)
0 packets with bad signature
0 packets with good signature
0 successful ECN handshakes
0 packets with ECN CE bit
0 packets ECN ECT(0) bit
udp:
16 datagrams received
0 with incomplete header
0 with bad data length field
0 with bad checksum
0 dropped due to no socket
2 broadcast/multicast datagrams dropped due to no socket
0 dropped due to full socket buffers
14 delivered
5 PCB hash misses
14 datagrams output
ip:
303 total packets received
0 bad header checksums
0 with size smaller than minimum
0 with data size < data length
0 with length > max ip packet size
0 with header length < data size
0 with data length < header length
0 with bad options
0 with incorrect version number
0 fragments received
0 fragments dropped (dup or out of space)
0 fragments dropped (out of ipqent)
0 malformed fragments dropped
0 fragments dropped after timeout
0 packets reassembled ok
302 packets for this host
0 packets for unknown/unsupported protocol
0 packets forwarded (0 packets fast forwarded)
1 packet not forwardable
0 redirects sent
0 packets no matching gif found
265 packets sent from this host
0 packets sent with fabricated ip header
0 output packets dropped due to no bufs, etc.
0 output packets discarded due to no route
0 output datagrams fragmented
0 fragments created
0 datagrams that can't be fragmented
0 datagrams with bad address in header
ip6:
6 total packets received
0 with size smaller than minimum
0 with data size < data length
0 with bad options
0 with incorrect version number
0 fragments received
0 fragments dropped (dup or out of space)
0 fragments dropped after timeout
0 fragments that exceeded limit
0 packets reassembled ok
6 packets for this host
0 packets forwarded
0 packets fast forwarded
0 fast forward flows
0 packets not forwardable
0 redirects sent
15 packets sent from this host
0 packets sent with fabricated ip header
0 output packets dropped due to no bufs, etc.
0 output packets discarded due to no route
0 output datagrams fragmented
0 fragments created
0 datagrams that can't be fragmented
0 packets that violated scope rules
0 multicast packets which we don't join
Input packet histogram:
UDP: 3
ICMP6: 3
Mbuf statistics:
0 one mbufs
6 one ext mbufs
0 two or more ext mbufs
0 packets whose headers are not continuous
0 tunneling packets that can't find gif
0 packets discarded due to too many headers
0 failures of source address selection
3 forward cache hit
2 forward cache miss
icmp6:
0 calls to icmp6_error
0 errors not generated because old message was icmp6 or so
0 errors not generated because of rate limitation
Output packet histogram:
multicast listener report: 8
router solicitation: 1
neighbor solicitation: 3
0 messages with bad code fields
0 messages < minimum length
0 bad checksums
0 messages with bad length
Input packet histogram:
router advertisement: 1
neighbor advertisement: 2
Histogram of error messages to be generated:
0 no route
0 administratively prohibited
0 beyond scope
0 address unreachable
0 port unreachable
0 packet too big
0 time exceed transit
0 time exceed reassembly
0 erroneous header field
0 unrecognized next header
0 unrecognized option
0 redirect
0 unknown
0 message responses generated
0 messages with too many ND options
0 messages with bad ND options
0 bad neighbor solicitation messages
0 bad neighbor advertisement messages
0 bad router solicitation messages
0 bad router advertisement messages
0 router advertisement routes dropped
0 bad redirect messages
0 path MTU changes
tcp6:
250 packets sent
170 data packets (33646 bytes)
0 data packets (0 bytes) retransmitted
70 ack-only packets (197 delayed)
0 URG only packets
0 window probe packets
1 window update packet
9 control packets
0 send attempts resulted in self-quench
284 packets received
163 acks (for 33649 bytes)
1 duplicate ack
0 acks for unsent data
250 packets (29579 bytes) received in-sequence
0 completely duplicate packets (0 bytes)
0 old duplicate packets
0 packets with some dup. data (0 bytes duped)
0 out-of-order packets (0 bytes)
0 packets (0 bytes) of data after window
0 window probes
2 window update packets
0 packets received after close
9 discarded for bad checksums
0 discarded for bad header offset fields
0 discarded because packet too short
2 connection requests
2 connection accepts
4 connections established (including accepts)
7 connections closed (including 0 drops)
0 embryonic connections dropped
0 delayed frees of tcpcb
165 segments updated rtt (of 161 attempts)
5 retransmit timeouts
0 connections dropped by rexmit timeout
0 persist timeouts (resulting in 0 dropped connections)
0 keepalive timeouts
0 keepalive probes sent
0 connections dropped by keepalive
0 correct ACK header predictions
100 correct data packet header predictions
4 PCB hash misses
0 dropped due to no socket
0 connections drained due to memory shortage
1 PMTUD blackhole detected
0 bad connection attempts
2 SYN cache entries added
0 hash collisions
2 completed
0 aborted (no space to build PCB)
0 timed out
0 dropped due to overflow
0 dropped due to bucket overflow
0 dropped due to RST
0 dropped due to ICMP unreachable
2 delayed free of SYN cache entries
0 SYN,ACKs retransmitted
0 duplicate SYNs received for entries already in the cache
0 SYNs dropped (no route or no space)
0 packets with bad signature
0 packets with good signature
0 successful ECN handshakes
0 packets with ECN CE bit
0 packets ECN ECT(0) bit
udp6:
3 datagrams received
0 with incomplete header
0 with bad data length field
0 with bad checksum
0 with no checksum
0 dropped due to no socket
0 multicast datagrams dropped due to no socket
0 dropped due to full socket buffers
3 delivered
3 datagrams output
pim6:
0 messages received
0 messages received with too few bytes
0 messages received with bad checksum
0 messages received with bad version
0 registers received
0 bad registers received
0 registers sent
rip6:
0 messages received
0 checksum calculations on inbound
0 messages with bad checksum
0 messages dropped due to no socket
0 multicast messages dropped due to no socket
0 messages dropped due to full socket buffers
0 delivered
0 datagrams output
arp:
4 packets sent
0 reply packets
4 request packets
13 packets received
3 reply packets
10 valid request packets
10 broadcast/multicast packets
0 packets with unknown protocol type
0 packets with bad (short) length
0 packets with null target IP address
0 packets with null source IP address
0 could not be mapped to an interface
0 packets sourced from a local hardware address
0 packets with a broadcast source hardware address
0 duplicates for a local IP address
0 attempts to overwrite a static entry
0 packets received on wrong interface
0 entrys overwritten
0 changes in hardware address length
3 packets deferred pending ARP resolution
3 sent
0 dropped
0 failures to allocate llinfo
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