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How to show dropped packets per interface on Linux

 

How to show dropped packets per interface on Linux

How do I show dropped packets per interface on Linux working techniques from the command line choice? How can I decide why a Linux server is dropping packets?

We will use the ip command or netstat command or ethtool command to indicate dropped packets statistics per community interface on Linux. Allow us to see the right way to use each instructions listing dropped packets per interface.

Tutorial particulars
Problem Superior (rss)
Root privileges Sure
Necessities Linux with GCC compilers
Time Relies upon upon your expertise and state of affairs

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Displaying present dropped packets per interface on Linux utilizing the netstat

The netstat command is usually out of date. Substitute for netstat is ss and ip command. Nonetheless, netstat nonetheless out there on older Linux distros, that are in productions. Therefore, I’ll begin with netstat but when doable, use the ip/ss instruments. The syntax is:
netstat -i
netstat –interfaces

How to show dropped packets per interface on Linux

Displaying community stats per community interface on LInux

To show abstract statistics for every protocol, run:

netstat -s
netstat –statistics
Outputs:

Ip:
Forwarding: 1
101759568 whole packets obtained
70289211 forwarded
Zero incoming packets discarded
31287093 incoming packets delivered
136164545 requests despatched out
22 outgoing packets dropped
220 reassemblies required
110 packets reassembled okay
2364 fragments obtained okay
3345 fragments failed
4728 fragments created
Icmp:
295517 ICMP messages obtained
6 enter ICMP message failed
ICMP enter histogram:
vacation spot unreachable: 145
timeout in transit: 187
echo requests: 289750
echo replies: 5435
298725 ICMP messages despatched
Zero ICMP messages failed
ICMP output histogram:
vacation spot unreachable: 3408
echo requests: 5567
echo replies: 289750
IcmpMsg:
InType0: 5435
InType3: 145
InType8: 289750
InType11: 187
OutType0: 289750
OutType3: 3408
OutType8: 5567
Tcp:
19006 energetic connection openings
14619 passive connection openings
2268 failed connection makes an attempt
393 connection resets obtained
1 connections established
2215735 segments obtained
2511500 segments despatched out
6067 segments retransmitted
182 dangerous segments obtained
13173 resets despatched
Udp:
28543977 packets obtained
63 packets to unknown port obtained
287687 packet obtain errors
22106848 packets despatched
287687 obtain buffer errors
Zero ship buffer errors
UdpLite:
TcpExt:
10 invalid SYN cookies obtained
2264 resets obtained for embryonic SYN_RECV sockets
42 packets pruned from obtain queue due to socket buffer overrun
14095 TCP sockets completed time wait in quick timer
21 packetes rejected in established connections due to timestamp
16908 delayed acks despatched
13 delayed acks additional delayed due to locked socket
Fast ack mode was activated 4346 instances
756194 packet headers predicted
441344 acknowledgments not containing knowledge payload obtained
618096 predicted acknowledgments
TCPSackRecovery: 87
Detected reordering 418 instances utilizing SACK
TCPDSACKUndo: 1
14 congestion home windows recovered with out gradual begin after partial ack
TCPLostRetransmit: 3994
TCPSackFailures: 1
121 quick retransmits
Eight retransmits in gradual begin
TCPTimeouts: 5158
TCPLossProbes: 789
TCPLossProbeRecovery: 66
TCPSackRecoveryFail: 3
TCPBacklogCoalesce: 8617
TCPDSACKOldSent: 4359
TCPDSACKOfoSent: 1
TCPDSACKRecv: 127
3870 connections reset resulting from surprising knowledge
244 connections reset resulting from early person shut
487 connections aborted resulting from timeout
TCPDSACKIgnoredNoUndo: 33
TCPSackShifted: 37
TCPSackMerged: 115
TCPSackShiftFallback: 731
TCPRcvCoalesce: 225465
TCPOFOQueue: 29252
TCPOFOMerge: 1
TCPChallengeACK: 193
TCPSYNChallenge: 186
TCPAutoCorking: 26574
TCPFromZeroWindowAdv: 8
TCPToZeroWindowAdv: 8
TCPWantZeroWindowAdv: 37
TCPSynRetrans: 647
TCPOrigDataSent: 1526711
TCPACKSkippedSynRecv: 153
TCPKeepAlive: 53
TCPDelivered: 1539034
TCPAckCompressed: 2559
IpExt:
InNoRoutes: 16
InBcastPkts: 4
InOctets: 92596603587
OutOctets: 263001759492
InBcastOctets: 310
InNoECTPkts: 121775194
InECT1Pkts: 1
InECT0Pkts: 51506
InCEPkts: 25

Present tcp stats

netstat –statistics –tcp
netstat -s -t

Show udp stats

netstat –statistics –udp
netstat -s -u

Exhibiting dropped packets statistics per community interface on Linux utilizing the ip

Allow us to see the right way to see hyperlink gadget stats utilizing the ip command. The syntax is:
ip -s hyperlink
ip -s hyperlink present {interface}
ip -s hyperlink present eth0
How to show dropped packets per interface on Linux
On this instance show hyperlink stats for wg0:
ip -s hyperlink present wg0

4: wg0: mtu 1420 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
hyperlink/none
RX: bytes packets errors dropped overrun mcast
1889086196 11451163 8413 62869 Zero 0
TX: bytes packets errors dropped service collsns
56342032204 41609374 0 5685 Zero 0

It’s clear that TX is Transmit and RX is Obtain. Wireguard creates the wg0 interface. So both Wireguard or firewall dropping packets as per coverage.

Queries the desired community gadget for NIC- and driver-specific statistics with ethtool

Go the -S or –statistics choice to show stats. Once more the syntax is simple:
ethtool -S
ethtool -S eth0

NIC statistics:
rx_queue_0_packets: 94804582
rx_queue_0_bytes: 92123064799
rx_queue_0_drops: 0
rx_queue_0_xdp_packets: 0
rx_queue_0_xdp_tx: 0
rx_queue_0_xdp_redirects: 0
rx_queue_0_xdp_drops: 0
rx_queue_0_kicks: 1499
tx_queue_0_packets: 94616365
tx_queue_0_bytes: 93565559918
tx_queue_0_xdp_tx: 0
tx_queue_0_xdp_tx_drops: 0
tx_queue_0_kicks: 40246533

Another choice is to straight question the /proc/web/dev file both utilizing the cat command or column command:
cat /proc/web/dev
column -t /proc/web/dev
And that is what we see:

Inter-| Obtain | Transmit
face |bytes packets errs drop fifo body compressed multicast|bytes packets errs drop fifo colls service compressed
eth0: 92123116754 94805122 Zero Zero Zero Zero Zero 0 93565689124 94617058 Zero Zero Zero Zero Zero 0
wg0: 1889086196 11451163 8413 62869 0 8413 Zero 0 56342032204 41609374 0 5685 Zero Zero Zero 0
lo: 52141452 150908 Zero Zero Zero Zero Zero 0 52141452 150908 Zero Zero Zero Zero Zero 0
tun0: 1650631998 16914416 Zero Zero Zero Zero Zero 0 30143956312 22000354 0 660246 Zero Zero Zero 0

Discovering out why a Linux server is dropping packets

We have to use dropwatch:

It’s a mission I began in an effort to enhance the flexibility for builders and system administrator to diagnose issues within the Linux Networking stack, particularly in our skill to diagnose the place packets are getting dropped.

Constructing dropwatch

Set up required instruments, libs and gcc compiler assortment on Ubuntu or Debian Linux:
sudo apt-get set up libpcap-dev libnl-3-dev libnl-genl-3-dev binutils-dev libreadline6-dev autoconf libtool pkg-config build-essential
Subsequent, clone the repo after which compile it:
git clone https://github.com/nhorman/dropwatch
cd dropwatch
./autogen.sh
./configure
make
make set up
Session:

Making set up in src
make[1]: Coming into listing ‘/tmp/dropwatch/src’
make[2]: Coming into listing ‘/tmp/dropwatch/src’
/usr/bin/mkdir -p ‘/usr/native/bin’
/bin/bash ../libtool –mode=set up /usr/bin/set up -c dropwatch dwdump ‘/usr/native/bin’
libtool: set up: /usr/bin/set up -c dropwatch /usr/native/bin/dropwatch
libtool: set up: /usr/bin/set up -c dwdump /usr/native/bin/dwdump
make[2]: Nothing to be completed for ‘install-data-am’.
make[2]: Leaving listing ‘/tmp/dropwatch/src’
make[1]: Leaving listing ‘/tmp/dropwatch/src’
Making set up in doc
make[1]: Coming into listing ‘/tmp/dropwatch/doc’
make[2]: Coming into listing ‘/tmp/dropwatch/doc’
make[2]: Nothing to be completed for ‘install-exec-am’.
/usr/bin/mkdir -p ‘/usr/native/share/man/man1’
/usr/bin/set up -c -m 644 dropwatch.1 ‘/usr/native/share/man/man1’
make[2]: Leaving listing ‘/tmp/dropwatch/doc’
make[1]: Leaving listing ‘/tmp/dropwatch/doc’
Making set up in assessments
make[1]: Coming into listing ‘/tmp/dropwatch/assessments’
make[2]: Coming into listing ‘/tmp/dropwatch/assessments’
make[2]: Nothing to be completed for ‘install-exec-am’.
make[2]: Nothing to be completed for ‘install-data-am’.
make[2]: Leaving listing ‘/tmp/dropwatch/assessments’
make[1]: Leaving listing ‘/tmp/dropwatch/assessments’
make[1]: Coming into listing ‘/tmp/dropwatch’
make[2]: Coming into listing ‘/tmp/dropwatch’
make[2]: Nothing to be completed for ‘install-exec-am’.
make[2]: Nothing to be completed for ‘install-data-am’.
make[2]: Leaving listing ‘/tmp/dropwatch’
make[1]: Leaving listing ‘/tmp/dropwatch’

Run it as follows:
# dropwatch -l kas
How to show dropped packets per interface on Linux
You see nf_hook_slow or icmpv6_rcv are Linux kernel features. It means I want to look Linux kernel timber and see what’s going on. Naturally, you have to perceive C programming and have an excellent understanding of Linux kernel internals together with TCP/IP stack. Now, you know the way to see if packets are dropped on the IP layer, the hyperlink layer, the UDP/TCP layer, or the appliance layer. If packets are dropped in TCP/IP, we have to look into the Linux kernel supply code documentation. See man web page and supply code of dropwatch for futher info:
man dropwatch
I might additionally recommend making an attempt out tcpdump to dump site visitors on a community interface. Typically it provides hints about packets and simply analyzed in wireshark device:
man tcpdump

Conclusion

You realized about varied Linux instructions to see packet loss on Linux per-interface, together with glorious instruments corresponding to dropwatch. We will additionally use Linux profiling with efficiency counters utility referred to as perf. Try perf examples for additional info.

🐧 Get the newest tutorials on SysAdmin, Linux/Unix, Open Supply/DevOps matters:

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