{"id":16585800,"url":"https://github.com/numtostr/shooter","last_synced_at":"2026-03-07T08:01:57.472Z","repository":{"id":103557142,"uuid":"261091449","full_name":"numToStr/shooter","owner":"numToStr","description":"a Docker + Kubernetes network trouble-shooting swiss-army container","archived":false,"fork":false,"pushed_at":"2020-05-04T05:53:08.000Z","size":194,"stargazers_count":0,"open_issues_count":0,"forks_count":0,"subscribers_count":3,"default_branch":"netshoot","last_synced_at":"2025-03-06T06:32:24.096Z","etag":null,"topics":[],"latest_commit_sha":null,"homepage":null,"language":"Dockerfile","has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":"apache-2.0","status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/numToStr.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":"LICENSE","code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null}},"created_at":"2020-05-04T05:50:59.000Z","updated_at":"2020-05-04T05:52:52.000Z","dependencies_parsed_at":null,"dependency_job_id":"2bd338db-81b7-4144-9313-2ad38d757a62","html_url":"https://github.com/numToStr/shooter","commit_stats":null,"previous_names":[],"tags_count":0,"template":false,"template_full_name":null,"purl":"pkg:github/numToStr/shooter","repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/numToStr%2Fshooter","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/numToStr%2Fshooter/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/numToStr%2Fshooter/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/numToStr%2Fshooter/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/numToStr","download_url":"https://codeload.github.com/numToStr/shooter/tar.gz/refs/heads/netshoot","sbom_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/numToStr%2Fshooter/sbom","scorecard":null,"host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":286080680,"owners_count":30209796,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2026-03-07T05:23:27.321Z","status":"ssl_error","status_checked_at":"2026-03-07T05:00:17.256Z","response_time":53,"last_error":"SSL_read: unexpected eof while reading","robots_txt_status":"success","robots_txt_updated_at":"2025-07-24T06:49:26.215Z","robots_txt_url":"https://github.com/robots.txt","online":false,"can_crawl_api":true,"host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":[],"created_at":"2024-10-11T22:49:35.893Z","updated_at":"2026-03-07T08:01:57.426Z","avatar_url":"https://github.com/numToStr.png","language":"Dockerfile","funding_links":[],"categories":[],"sub_categories":[],"readme":"## netshoot: a Docker + Kubernetes network trouble-shooting swiss-army container\n\n```\n                    dP            dP                           dP\n                    88            88                           88\n88d888b. .d8888b. d8888P .d8888b. 88d888b. .d8888b. .d8888b. d8888P\n88'  `88 88ooood8   88   Y8ooooo. 88'  `88 88'  `88 88'  `88   88\n88    88 88.  ...   88         88 88    88 88.  .88 88.  .88   88\ndP    dP `88888P'   dP   `88888P' dP    dP `88888P' `88888P'   dP\n```\n\n**Purpose:** Docker and Kubernetes network troubleshooting can become complex. With proper understanding of how Docker and Kubernetes networking works and the right set of tools, you can troubleshoot and resolve these networking issues. The `netshoot` container has a set of powerful networking tshooting tools that can be used to troubleshoot Docker networking issues. Along with these tools come a set of use-cases that show how this container can be used in real-world scenarios.\n\n**Network Namespaces:** Before starting to use this tool, it's important to go over one key topic: **Network Namespaces**. Network namespaces provide isolation of the system resources associated with networking. Docker uses network and other type of namespaces (`pid`,`mount`,`user`..etc) to create an isolated environment for each container. Everything from interfaces, routes, and IPs is completely isolated within the network namespace of the container. \n\nKubernetes also uses network namespaces. Kubelets creates a network namespace per pod where all containers in that pod share that same network namespace (eths,IP, tcp sockets...etc). This is a key difference between Docker containers and Kubernetes pods.\n\nCool thing about namespaces is that you can switch between them. You can enter a different container's network namespace, perform some troubleshooting on its network's stack with tools that aren't even installed on that container. Additionally, `netshoot` can be used to troubleshoot the host itself by using the host's network namespace. This allows you to perform any troubleshooting without installing any new packages directly on the host or your application's package. \n\n* **Container's Network Namespace:** If you're having networking issues with your application's container, you can launch `netshoot` with that container's network namespace like this :\n\n`$ docker run -it --net container:\u003ccontainer_name\u003e nicolaka/netshoot`\n\n* **Host's Network Namespace:** If you think the networking issue is on the host itself, you can launch `netshoot` with that host's network namespace. This is how:\n \n`$ docker run -it --net host nicolaka/netshoot`\n\n* **Network's Network Namespace:** If you want to troubleshoot a Docker network, you can enter the network's namespace using `nsenter`. This is explained in the `nsenter` section below.\n\n**Kubernetes**\n\nIf you want to spin up a throw away container for debugging.\n\n`$ kubectl run --generator=run-pod/v1 tmp-shell --rm -i --tty --image nicolaka/netshoot -- /bin/bash`\n\nAnd if you want to spin up a container on the host's network namespace.\n\n`$ kubectl run tmp-shell --generator=run-pod/v1 --rm -i --tty --overrides='{\"spec\": {\"hostNetwork\": true}}'  --image nicolaka/netshoot  -- /bin/bash`\n\n**Network Problems** \n\nMany network issues could result in application performance degradation. Some of those issues could be related to the underlying networking infrastructure(underlay). Others could be related to misconfiguration at the host or Docker level. Let's take a look at common networking issues:\n\n* latency\n* routing \n* DNS resolution\n* firewall \n* incomplete ARPs\n\nTo troubleshoot these issues, `netshoot` includes a set of powerful tools as recommended by this diagram. \n\n![](http://www.brendangregg.com/Perf/linux_observability_tools.png)\n\n\n**Included Packages:** The following packages are included in `netshoot`. We'll go over some with some sample use-cases.\n\n    apache2-utils\n    bash\n    bind-tools\n    bird\n    bridge-utils\n    busybox-extras\n    calicoctl\n    conntrack-tools\n    ctop\n    curl\n    dhcping\n    drill\n    ethtool\n    file\n    fping\n    iftop\n    iperf\n    iproute2\n    ipset\n    iptables\n    iptraf-ng\n    iputils\n    ipvsadm\n    jq\n    libc6-compat\n    liboping\n    mtr\n    net-snmp-tools\n    netcat-openbsd\n    netgen\n    nftables\n    ngrep\n    nmap\n    nmap-nping\n    openssl\n    py-crypto\n    py2-virtualenv\n    python2\n    scapy\n    socat\n    strace\n    tcpdump\n    tcptraceroute\n    util-linux\n    vim\n\n## **Docker EE 2.0 + Kubernetes Use Cases:** \nHere's a list of use-cases that can help you understand when and how to use this container to solve networking issues in your Docker cluster. Please feel free to add your own use-case where you used `netshoot` to investigate, trouble-shoot, or just learn more about your environment!!!\n\n\n## Managing Kubernetes Calico CNI with calicoctl\n\nIn Docker Enterprise Edition, and in so many Kubernetes-based solutions, [Calico](https://www.projectcalico.org/) is used as the default CNI plugin of choice. This means that all the pod networking related resources ( IP assignment, routing, network policies, etc..) is handled by Calico. [calicoctl](https://github.com/projectcalico/calicoctl) is a cli tool to makes it easy to manage Calico network and security policy, as well as other Calico configurations. The calicoctl tool talks directly to `etcd`, so it's often not possible or recommended to expose etcd outside of the Kubernetes cluster. A recommended way to use calicoctl is to run it on a the master node inside the cluster. \n\nAssuming you are running Docker EE 2.0 (although this should work on any Kuberenetes cluster with Calico installed), run the `netshoot` as a deployment using [this deployment](configs/netshoot-calico.yaml). This deployment will use the `kube-system` namespace.\n\n```\n# Note: This step assumes you loaded UCP client bundle and have kubectl working as expected.\n🐳  → kubectl apply -f netshoot-calico.yaml\n```\n\nThis deployment will deploy a single pod on a master node and automatically load up etcd certs so you can easily start using calicoctl. Now it's time to exec into the pod:\n\n```\n🐳  → kubectl get pod --selector=app=netshoot -n kube-system\nNAME                                      READY     STATUS    RESTARTS   AGE\nnetshoot-calico-deploy-57b8896459-rzqz4   1/1       Running   0          1h\n```\n\nNow exec into this pod and use the calicoctl directly without any further configurations! Full documentations on using the calicoctl tool is found [here](https://docs.projectcalico.org/v3.1/reference/calicoctl/commands/).\n\n```\n🐳  → kubectl exec -it -n kube-system netshoot-calico-deploy-57b8896459-rzqz4 -- /bin/bash -l\n                    dP            dP                           dP\n                    88            88                           88\n88d888b. .d8888b. d8888P .d8888b. 88d888b. .d8888b. .d8888b. d8888P\n88'  `88 88ooood8   88   Y8ooooo. 88'  `88 88'  `88 88'  `88   88\n88    88 88.  ...   88         88 88    88 88.  .88 88.  .88   88\ndP    dP `88888P'   dP   `88888P' dP    dP `88888P' `88888P'   dP\n\nWelcome to Netshoot! (github.com/nicolaka/netshoot)\nroot @ /\n [1] 🐳  → calicoctl get wep\nWORKLOAD                            NODE              NETWORKS             INTERFACE\nnginx-deployment-569477d6d8-98xv5   ip-10-56-14-210   192.168.134.207/32   calia756b40818a\nnetshoot-deploy-6bffc797bf-cfgpp    ip-10-56-17-161   192.168.63.80/32     cali50d3753ec26\nnginx-deployment-569477d6d8-6klz6   ip-10-56-17-161   192.168.63.79/32     caliaef53a8ccae\n\n\nroot @ /\n [2] 🐳  → calicoctl get ippool\nNAME                  CIDR\ndefault-ipv4-ippool   192.168.0.0/16\n\n\nroot @ /\n [3] 🐳  → calicoctl get bgpconfig -o yaml\napiVersion: projectcalico.org/v3\nitems:\n- apiVersion: projectcalico.org/v3\n  kind: BGPConfiguration\n  metadata:\n    creationTimestamp: 2018-05-03T18:04:13Z\n    name: default\n    resourceVersion: \"4519634\"\n    uid: 631aa7d6-4efc-11e8-92d5-06982eb5f90e\n  spec:\n    asNumber: 63400\n    logSeverityScreen: Info\n    nodeToNodeMeshEnabled: false\nkind: BGPConfigurationList\nmetadata:\n  resourceVersion: \"6152496\"\n```\n\n##**Docker + Swarm Use Cases:** \n\n## iperf \n\nPurpose : test networking performance between two containers/hosts. \n\nCreate Overlay network:\n\n```\n$ docker network create -d overlay perf-test\n```\nLaunch two containers:\n\n```\n🐳  → docker service create --name perf-test-a --network perf-test nicolaka/netshoot iperf -s -p 9999\n7dkcckjs0g7b4eddv8e5ez9nv\n\n\n🐳  → docker service create --name perf-test-b --network perf-test nicolaka/netshoot iperf -c perf-test-a -p 9999\n2yb6fxls5ezfnav2z93lua8xl\n\n\n\n 🐳  → docker service ls\nID            NAME         REPLICAS  IMAGE              COMMAND\n2yb6fxls5ezf  perf-test-b  1/1       nicolaka/netshoot  iperf -c perf-test-a -p 9999\n7dkcckjs0g7b  perf-test-a  1/1       nicolaka/netshoot  iperf -s -p 9999\n\n\n\n🐳  → docker ps\nCONTAINER ID        IMAGE                      COMMAND                  CREATED             STATUS              PORTS               NAMES\nce4ff40a5456        nicolaka/netshoot:latest   \"iperf -s -p 9999\"       31 seconds ago      Up 30 seconds                           perf-test-a.1.bil2mo8inj3r9nyrss1g15qav\n\n🐳  → docker logs ce4ff40a5456\n------------------------------------------------------------\nServer listening on TCP port 9999\nTCP window size: 85.3 KByte (default)\n------------------------------------------------------------\n[  4] local 10.0.3.3 port 9999 connected with 10.0.3.5 port 35102\n[ ID] Interval       Transfer     Bandwidth\n[  4]  0.0-10.0 sec  32.7 GBytes  28.1 Gbits/sec\n[  5] local 10.0.3.3 port 9999 connected with 10.0.3.5 port 35112\n\n```\n\n## tcpdump\n\n**tcpdump** is a powerful and common packet analyzer that runs under the command line. It allows the user to display TCP/IP and other packets being transmitted or received over an attached network interface. \n\n```\n# Continuing on the iperf example. Let's launch netshoot with perf-test-a's container network namespace.\n\n🐳  → docker run -it --net container:perf-test-a.1.0qlf1kaka0cq38gojf7wcatoa  nicolaka/netshoot \n\n# Capturing packets on eth0 and tcp port 9999.\n\n/ # tcpdump -i eth0 port 9999 -c 1 -Xvv\ntcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes\n23:14:09.771825 IP (tos 0x0, ttl 64, id 60898, offset 0, flags [DF], proto TCP (6), length 64360)\n    10.0.3.5.60032 \u003e 0e2ccbf3d608.9999: Flags [.], cksum 0x1563 (incorrect -\u003e 0x895d), seq 222376702:222441010, ack 3545090958, win 221, options [nop,nop,TS val 2488870 ecr 2488869], length 64308\n\t0x0000:  4500 fb68 ede2 4000 4006 37a5 0a00 0305  E..h..@.@.7.....\n\t0x0010:  0a00 0303 ea80 270f 0d41 32fe d34d cb8e  ......'..A2..M..\n\t0x0020:  8010 00dd 1563 0000 0101 080a 0025 fa26  .....c.......%.\u0026\n\t0x0030:  0025 fa25 0000 0000 0000 0001 0000 270f  .%.%..........'.\n\t0x0040:  0000 0000 0000 0000 ffff d8f0 3435 3637  ............4567\n\t0x0050:  3839 3031 3233 3435 3637 3839 3031 3233  8901234567890123\n\t0x0060:  3435 3637 3839 3031 3233 3435 3637 3839  4567890123456789\n\t0x0070:  3031 3233 3435 3637 3839 3031 3233 3435  0123456789012345\n\t0x0080:  3637 3839 3031 3233 3435 3637 3839 3031  6789012345678901\n\t0x0090:  3233 3435 3637 3839 3031 3233 3435 3637  2345678901234567\n\t0x00a0:  3839 3031 3233 3435 3637 3839 3031 3233  8901234567890123\n\t0x00b0:  3435 3637 3839 3031 3233 3435 3637 3839  4567890123456789\n\t0x00c0:  3031 3233 3435 3637 3839 3031 3233 3435  0123456789012345\n\t0x00d0:  3637 3839 3031 3233 3435 3637 3839 3031  6789012345678901\n\t0x00e0:  3233 3435 3637 3839 3031 3233 3435 3637  2345678901234567\n\t0x00f0:  3839 3031 3233 3435 3637 3839 3031 3233  8901234567890123\n\t0x0100:  3435 3637 3839 3031 3233 3435 3637 3839  4567890123456789\n\t\n```\n\nMore info on `tcpdump` can be found [here](http://www.tcpdump.org/tcpdump_man.html).\n\n\n\n## netstat\n\nPurpose: `netstat` is a useful tool for checking your network configuration and activity. \n\nContinuing on from `iperf` example. Let's use `netstat` to confirm that it's listening on port `9999`. \n\n\n```\n🐳  → docker run -it --net container:perf-test-a.1.0qlf1kaka0cq38gojf7wcatoa  nicolaka/netshoot \n\n/ # netstat -tulpn\nActive Internet connections (only servers)\nProto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name\ntcp        0      0 127.0.0.11:46727        0.0.0.0:*               LISTEN      -\ntcp        0      0 0.0.0.0:9999            0.0.0.0:*               LISTEN      -\nudp        0      0 127.0.0.11:39552        0.0.0.0:*                           -\n```\n\n##  nmap\n`nmap` (\"Network Mapper\") is an open source tool for network exploration and security auditing. It is very useful for scanning to see which ports are open between a given set of hosts. This is a common thing to check for when installing Swarm or UCP because a range of ports is required for cluster communication. The command analyzes the connection pathway between the host where `nmap` is running and the given target address.\n\n```\n🐳  → docker run -it --privileged nicolaka/netshoot nmap -p 12376-12390 -dd 172.31.24.25\n\n...\nDiscovered closed port 12388/tcp on 172.31.24.25\nDiscovered closed port 12379/tcp on 172.31.24.25\nDiscovered closed port 12389/tcp on 172.31.24.25\nDiscovered closed port 12376/tcp on 172.31.24.25\n...\n```\nThere are several states that ports will be discovered as:\n\n- `open`: the pathway to the port is open and there is an application listening on this port.\n- `closed`: the pathway to the port is open but there is no application listening on this port.\n- `filtered`: the pathway to the port is closed, blocked by a firewall, routing rules, or host-based rules.\n\n\n## iftop\n\nPurpose: iftop does for network usage what top does for CPU usage. It listens to network traffic on a named interface and displays a table of current bandwidth usage by pairs of hosts.\n\nContinuing the `iperf` example.\n\n```\n → docker ps\nCONTAINER ID        IMAGE                      COMMAND                  CREATED             STATUS              PORTS               NAMES\nce4ff40a5456        nicolaka/netshoot:latest   \"iperf -s -p 9999\"       5 minutes ago       Up 5 minutes                            perf-test-a.1.bil2mo8inj3r9nyrss1g15qav\n\n🐳  → docker run -it --net container:perf-test-a.1.bil2mo8inj3r9nyrss1g15qav nicolaka/netshoot iftop -i eth0\n\n```\n\n![iftop.png](img/iftop.png)\n\n\n## drill\n\nPurpose: drill is a tool\tto designed to get all sorts of information out of the DNS.\n\nContinuing the `iperf` example, we'll use `drill` to understand how services' DNS is resolved in Docker. \n\n\n```\n🐳  → docker run -it --net container:perf-test-a.1.bil2mo8inj3r9nyrss1g15qav nicolaka/netshoot drill -V 5 perf-test-b\n;; -\u003e\u003eHEADER\u003c\u003c- opcode: QUERY, rcode: NOERROR, id: 0\n;; flags: rd ; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0\n;; QUESTION SECTION:\n;; perf-test-b.\tIN\tA\n\n;; ANSWER SECTION:\n\n;; AUTHORITY SECTION:\n\n;; ADDITIONAL SECTION:\n\n;; Query time: 0 msec\n;; WHEN: Thu Aug 18 02:08:47 2016\n;; MSG SIZE  rcvd: 0\n;; -\u003e\u003eHEADER\u003c\u003c- opcode: QUERY, rcode: NOERROR, id: 52723\n;; flags: qr rd ra ; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0\n;; QUESTION SECTION:\n;; perf-test-b.\tIN\tA\n\n;; ANSWER SECTION:\nperf-test-b.\t600\tIN\tA\t10.0.3.4 \u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c Service VIP\n\n;; AUTHORITY SECTION:\n\n;; ADDITIONAL SECTION:\n\n;; Query time: 1 msec\n;; SERVER: 127.0.0.11 \u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c Local resolver \n;; WHEN: Thu Aug 18 02:08:47 2016\n;; MSG SIZE  rcvd: 56\n```\n\n## netcat\n\nPurpose: a simple Unix utility that reads and writes data across network connections, using the TCP or UDP protocol. It's useful for testing and troubleshooting TCP/UDP connections. If there's a firewall rule blocking certain ports, `netcat` can be used to detect\n\n```\n🐳  →  docker network create -d overlay my-ovl\n55rohpeerwqx8og4n0byr0ehu\n\n🐳  → docker service create --name service-a --network my-ovl -p 8080:8080 nicolaka/netshoot nc -l 8080\nbnj517hh4ylpf7ewawsp9unrc\n\n🐳  → docker service create --name service-b --network my-ovl nicolaka/netshoot nc -vz service-a 8080\n3xv1ukbd3kr03j4uybmmlp27j\n\n🐳  → docker logs service-b.1.0c5wy4104aosovtl1z9oixiso\nConnection to service-a 8080 port [tcp/http-alt] succeeded!\n\n```\n##  netgen\n`netgen` is a simple [script](netgen.sh) that will generate a packet of data between containers periodically using `netcat`. It's purpose is to use the generated traffic to demonstrate different features of the networking stack.\n\n\n`netgen \u003chost\u003e \u003cip\u003e` will create a `netcat` server and client listening and sending to the same port.\n\nUsing `netgen` with `docker run`:\n\n```\n🐳  →  docker network create -d bridge br\n01b167971453700cf0a40d7e1a0dc2b0021e024bbb119541cc8c1858343c9cfc\n\n🐳  →  docker run -d --rm --net br --name c1 nicolaka/netshoot netgen c2 5000\n8c51eb2100c35d14244dcecb80839c780999159985415a684258c7154ec6bd42\n\n🐳  →  docker run -it --rm --net br --name c2 nicolaka/netshoot netgen c1 5000\nListener started on port 5000\nSending traffic to c1 on port 5000 every 10 seconds\nSent 1 messages to c1:5000\nSent 2 messages to c1:5000\n\n🐳  →  sudo tcpdump -vvvn -i eth0 port 5000\n...\n```\n\nUsing `netgen` with `docker services`:\n\n```\n🐳  →  docker network create -d overlay ov\n01b167971453700cf0a40d7e1a0dc2b0021e024bbb119541cc8c1858343c9cfc\n\n🐳  →  docker service create --network ov --replicas 3 --name srvc netshoot netgen srvc 5000\ny93t8mb9wgzsc27f7l2rdu5io\n\n🐳  →  docker service logs srvc\nsrvc.1.vwklts5ybq5w@moby    | Listener started on port 5000\nsrvc.1.vwklts5ybq5w@moby    | Sending traffic to srvc on port 5000 every 10 seconds\nsrvc.1.vwklts5ybq5w@moby    | Sent 1 messages to srvc:5000\nsrvc.3.dv4er00inlxo@moby    | Listener started on port 5000\nsrvc.2.vu47gf0sdmje@moby    | Listener started on port 5000\n...\n\n\n🐳  →  sudo tcpdump -vvvn -i eth0 port 5000\n...\n```\n\n\n##  iproute2\n\npurpose: a collection of utilities for controlling TCP / IP networking and traffic control in Linux.\n\n```\n# Sample routing and arp table of the docker host.\n\n🐳  → docker run -it --net host nicolaka/netshoot\n\n/ # ip route show\ndefault via 192.168.65.1 dev eth0  metric 204\n172.17.0.0/16 dev docker0  proto kernel  scope link  src 172.17.0.1\n172.19.0.0/16 dev br-fd694678f5c3  proto kernel  scope link  src 172.19.0.1 linkdown\n172.20.0.0/16 dev docker_gwbridge  proto kernel  scope link  src 172.20.0.1\n172.21.0.0/16 dev br-0d73cc4ac114  proto kernel  scope link  src 172.21.0.1 linkdown\n172.22.0.0/16 dev br-1eb1f1e84df8  proto kernel  scope link  src 172.22.0.1 linkdown\n172.23.0.0/16 dev br-aafed4ec941f  proto kernel  scope link  src 172.23.0.1 linkdown\n192.168.65.0/29 dev eth0  proto kernel  scope link  src 192.168.65.2\n\n/ # ip neigh show\n192.168.65.1 dev eth0 lladdr f6:16:36:bc:f9:c6 STALE\n172.17.0.7 dev docker0 lladdr 02:42:ac:11:00:07 STALE\n172.17.0.6 dev docker0 lladdr 02:42:ac:11:00:06 STALE\n172.17.0.5 dev docker0 lladdr 02:42:ac:11:00:05 STALE\n```\n\nMore info on `iproute2` [here](http://lartc.org/howto/lartc.iproute2.tour.html)\n\n## nsenter\n\nPurpose: `nsenter` is a powerful tool allowing you to enter into any namespaces. `nsenter` is available inside `netshoot` but requires `netshoot` to be run as a privileged container. Additionally, you may want to mount the `/var/run/docker/netns` directory to be able to enter any network namespace including bridge and overlay networks. \n\n\nWith `docker run --name container-B --net container:container-A `, docker uses `container-A`'s network namespace ( including interfaces and routes) when creating `container-B`. This approach is helpful for troubleshooting network issues at the container level. To troubleshoot network issues at the bridge or overlay network level, you need to enter the `namespace` of the network _itself_. `nsenter` allows you to do that. \n\nFor example, if we wanted to check the L2 forwarding table for a overlay network. We need to enter the overlay network namespace and use same tools in `netshoot` to check these entries.  The following examples go over some use cases for using `nsenter` to understand what's happening within a docker network ( overlay in this case).\n\n```\n# Creating an overlay network\n🐳  → docker network create -d overlay nsenter-test\n9tp0f348donsdj75pktssd97b\n\n# Launching a simple busybox service with 3 replicas\n🐳  → docker service create --name nsenter-l2-table-test --replicas 3 --network nsenter-test busybox ping localhost\n3692i3q3u8nephdco2c10ro4c\n\n# Inspecting the service\n🐳  → docker network inspect nsenter-test\n[\n    {\n        \"Name\": \"nsenter-test\",\n        \"Id\": \"9tp0f348donsdj75pktssd97b\",\n        \"Scope\": \"swarm\",\n        \"Driver\": \"overlay\",\n        \"EnableIPv6\": false,\n        \"IPAM\": {\n            \"Driver\": \"default\",\n            \"Options\": null,\n            \"Config\": [\n                {\n                    \"Subnet\": \"10.0.1.0/24\",\n                    \"Gateway\": \"10.0.1.1\"\n                }\n            ]\n        },\n        \"Internal\": false,\n        \"Containers\": {\n            \"0ebe0fab555d2e2ef2fcda634bef2071ad3f5842b06bd134b40f259ab9be4f13\": {\n                \"Name\": \"nsenter-l2-table-test.2.83uezc16jcaz2rp6cjwyf4605\",\n                \"EndpointID\": \"3064946bb0224a4b3647cefcba18dcbea71b90a2ba1c09212a7bc599ec1ed3eb\",\n                \"MacAddress\": \"02:42:0a:00:01:04\",\n                \"IPv4Address\": \"10.0.1.4/24\",\n                \"IPv6Address\": \"\"\n            },\n            \"55065360ac1c71638fdef50a073a661dec53b693409c5e09f8f854abc7dbb373\": {\n                \"Name\": \"nsenter-l2-table-test.1.4ryh3wmmv21nsrfwmilanypqq\",\n                \"EndpointID\": \"f81ae5f979d6c54f60636ca9bb2107d95ebf9a08f64786c549e87a66190f1b1f\",\n                \"MacAddress\": \"02:42:0a:00:01:03\",\n                \"IPv4Address\": \"10.0.1.3/24\",\n                \"IPv6Address\": \"\"\n            },\n            \"57eca277749bb01a488f0e6c4e91dc6720b7c8f08531536377b29a972971f54b\": {\n                \"Name\": \"nsenter-l2-table-test.3.9cuoq5m2ue1wi4lsw64k88tvz\",\n                \"EndpointID\": \"ff1a251ffd6c674cd5fd117386d1a197ab68b4ed708187035d91ff5bd5fe0251\",\n                \"MacAddress\": \"02:42:0a:00:01:05\",\n                \"IPv4Address\": \"10.0.1.5/24\",\n                \"IPv6Address\": \"\"\n            }\n        },\n        \"Options\": {\n            \"com.docker.network.driver.overlay.vxlanid_list\": \"260\"\n        },\n        \"Labels\": {}\n    }\n]\n\n# Launching netshoot in privileged mode\n 🐳  → docker run -it --rm -v /var/run/docker/netns:/var/run/docker/netns --privileged=true nicolaka/netshoot\n \n# Listing all docker-created network namespaces\n \n / # cd /var/run/docker/netns/\n/var/run/docker/netns # ls\n0b1b36d33313  1-9tp0f348do  14d1428c3962  645eb414b538  816b96054426  916dbaa7ea76  db9fd2d68a9b  e79049ce9994  f857b5c01ced\n1-9r17dodsxt  1159c401b8d8  1a508036acc8  7ca29d89293c  83b743f2f087  aeed676a57a5  default       f22ffa5115a0\n\n\n# The overlay network that we created had an id of 9tp0f348donsdj75pktssd97b. All overlay networks are named \u003cnumber\u003e-\u003cid\u003e. We can see it in the list as `1-9tp0f348do`. To enter it:\n\n/ # nsenter --net=/var/run/docker/netns/1-9tp0f348do sh\n\n# Now all the commands we issue are within that namespace. \n\n/ # ifconfig\nbr0       Link encap:Ethernet  HWaddr 02:15:B8:E7:DE:B3\n          inet addr:10.0.1.1  Bcast:0.0.0.0  Mask:255.255.255.0\n          inet6 addr: fe80::20ce:a5ff:fe63:437d%32621/64 Scope:Link\n          UP BROADCAST RUNNING MULTICAST  MTU:1450  Metric:1\n          RX packets:36 errors:0 dropped:0 overruns:0 frame:0\n          TX packets:18 errors:0 dropped:0 overruns:0 carrier:0\n          collisions:0 txqueuelen:0\n          RX bytes:2224 (2.1 KiB)  TX bytes:1348 (1.3 KiB)\n\nlo        Link encap:Local Loopback\n          inet addr:127.0.0.1  Mask:255.0.0.0\n          inet6 addr: ::1%32621/128 Scope:Host\n          UP LOOPBACK RUNNING  MTU:65536  Metric:1\n          RX packets:4 errors:0 dropped:0 overruns:0 frame:0\n          TX packets:4 errors:0 dropped:0 overruns:0 carrier:0\n          collisions:0 txqueuelen:1\n          RX bytes:336 (336.0 B)  TX bytes:336 (336.0 B)\n\nveth2     Link encap:Ethernet  HWaddr 02:15:B8:E7:DE:B3\n          inet6 addr: fe80::15:b8ff:fee7:deb3%32621/64 Scope:Link\n          UP BROADCAST RUNNING MULTICAST  MTU:1450  Metric:1\n          RX packets:9 errors:0 dropped:0 overruns:0 frame:0\n          TX packets:32 errors:0 dropped:0 overruns:0 carrier:0\n          collisions:0 txqueuelen:0\n          RX bytes:690 (690.0 B)  TX bytes:2460 (2.4 KiB)\n\nveth3     Link encap:Ethernet  HWaddr 7E:55:C3:5C:C2:78\n          inet6 addr: fe80::7c55:c3ff:fe5c:c278%32621/64 Scope:Link\n          UP BROADCAST RUNNING MULTICAST  MTU:1450  Metric:1\n          RX packets:13 errors:0 dropped:0 overruns:0 frame:0\n          TX packets:26 errors:0 dropped:0 overruns:0 carrier:0\n          collisions:0 txqueuelen:0\n          RX bytes:970 (970.0 B)  TX bytes:1940 (1.8 KiB)\n\nveth4     Link encap:Ethernet  HWaddr 72:95:AB:A1:6A:87\n          inet6 addr: fe80::7095:abff:fea1:6a87%32621/64 Scope:Link\n          UP BROADCAST RUNNING MULTICAST  MTU:1450  Metric:1\n          RX packets:14 errors:0 dropped:0 overruns:0 frame:0\n          TX packets:27 errors:0 dropped:0 overruns:0 carrier:0\n          collisions:0 txqueuelen:0\n          RX bytes:1068 (1.0 KiB)  TX bytes:2038 (1.9 KiB)\n\nvxlan1    Link encap:Ethernet  HWaddr EA:EC:1D:B1:7D:D7\n          inet6 addr: fe80::e8ec:1dff:feb1:7dd7%32621/64 Scope:Link\n          UP BROADCAST RUNNING MULTICAST  MTU:1450  Metric:1\n          RX packets:0 errors:0 dropped:0 overruns:0 frame:0\n          TX packets:0 errors:0 dropped:33 overruns:0 carrier:0\n          collisions:0 txqueuelen:0\n          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)\n\n# Let's check out the L2 forwarding table. These MAC addresses belong to the tasks/containers in this service. \n\n/ # bridge  fdb show br br0\n33:33:00:00:00:01 dev br0 self permanent\n01:00:5e:00:00:01 dev br0 self permanent\n33:33:ff:63:43:7d dev br0 self permanent\nea:ec:1d:b1:7d:d7 dev vxlan1 master br0 permanent\n02:15:b8:e7:de:b3 dev veth2 master br0 permanent\n33:33:00:00:00:01 dev veth2 self permanent\n01:00:5e:00:00:01 dev veth2 self permanent\n33:33:ff:e7:de:b3 dev veth2 self permanent\n7e:55:c3:5c:c2:78 dev veth3 master br0 permanent\n33:33:00:00:00:01 dev veth3 self permanent\n01:00:5e:00:00:01 dev veth3 self permanent\n33:33:ff:5c:c2:78 dev veth3 self permanent\n72:95:ab:a1:6a:87 dev veth4 master br0 permanent\n33:33:00:00:00:01 dev veth4 self permanent\n01:00:5e:00:00:01 dev veth4 self permanent\n33:33:ff:a1:6a:87 dev veth4 self permanent\n\n\n# ARP and routing tables. Note that an overlay network only routes traffic for that network. It only has a single route that matches the subnet of that network.\n\n/ # ip neigh show\n/ # ip route\n10.0.1.0/24 dev br0  proto kernel  scope link  src 10.0.1.1\n\n# Looks like the arp table is flushed. Let's ping some of the containers on this network.\n\n/ # ping 10.0.1.4\nPING 10.0.1.4 (10.0.1.4) 56(84) bytes of data.\n64 bytes from 10.0.1.4: icmp_seq=1 ttl=64 time=0.207 ms\n64 bytes from 10.0.1.4: icmp_seq=2 ttl=64 time=0.087 ms\n^C\n--- 10.0.1.4 ping statistics ---\n2 packets transmitted, 2 received, 0% packet loss, time 1002ms\nrtt min/avg/max/mdev = 0.087/0.147/0.207/0.060 ms\n\n/ # ip neigh show\n10.0.1.4 dev br0 lladdr 02:42:0a:00:01:04 REACHABLE\n\n# and using bridge-utils to show interfaces of the overlay network local bridge.\n\n/ # brctl show\nbridge name\tbridge id\t\tSTP enabled\tinterfaces\nbr0\t\t8000.0215b8e7deb3\tno\t\tvxlan1\n\t\t\t\t\t\t\tveth2\n\t\t\t\t\t\t\tveth3\n\t\t\t\t\t\t\tveth4\n\t\t\t\t\t\t\t\n```\n\n## CTOP\n\nctop is a free open source, simple and cross-platform top-like command-line tool for monitoring container metrics in real-time. It allows you to get an overview of metrics concerning CPU, memory, network, I/O for multiple containers and also supports inspection of a specific container.\n\nTo get data into ctop, you'll need to bind docker.sock into the netshoot container.\n\n```\n/ # docker run -it --rm -v /var/run/docker.sock:/var/run/docker.sock nicolaka/netshoot ctop\n```\n\n![ctop.png](img/ctop.png)\n\nIt will display running and existed containers with useful metrics to help troubleshoot resource issues; hit \"q\" to exit.\n\n\n## Feedback + Contribution\n\nFeel free to provide feedback and contribute networking troubleshooting tools and use-cases by opening PRs.\n\n\n\n\n\n\n\n \n\n\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fnumtostr%2Fshooter","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fnumtostr%2Fshooter","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fnumtostr%2Fshooter/lists"}