###### tags: `Study Circle Note`, `Docker in Action 2ed`

# Docker in Action 2ed 第四次 2021-07-24 - Ch5

## 討論

- overlay/underly 是不是剛好講相反
- underlay
> you can use underlay networks provided by the macvlan or ipvlan network drivers.
- overlay
> The overlay network driver is available on Docker engines where swarm mode is enabled.
- joined containers 是不是類似 host 模式到另一個 container 中？
- 有點不太一樣，joined container 是讓 container 共用同一個 network namespace
- [host mode](https://docs.docker.com/network/host/) 是讓 container 跟 host 使用同一個 namespace

- 推薦好文：
> 在 Linux 上目前其實也支援了非常多類型種類的 Virtual network interface
https://developers.redhat.com/blog/2018/10/22/introduction-to-linux-interfaces-for-virtual-networking
> [name=Jerry Wang

- 為何 `/etc/resolv.conf` 會是 127.0.0.11 ?
> Docker 篡改的，[程式碼似乎在這](https://github.com/moby/moby/blob/6317d7467a858de28531516fac75d1b230d024dd/container/container_unix.go#L63)，詳細[過程說明](https://collabnix.com/how-service-discovery-works-under-docker-1-12/)

## 補充 Lab

1. Install docker[1] with Ubuntu 20.04 server. Here is the docker version.

    $ docker version
    Client: Docker Engine - Community
    Version:           20.10.7
    API version:       1.41
    Go version:        go1.13.15
    Git commit:        f0df350
    Built:             Wed Jun  2 11:56:38 2021
    OS/Arch:           linux/amd64
    Context:           default
    Experimental:      true

    Server: Docker Engine - Community
    Engine:
    Version:          20.10.7
    API version:      1.41 (minimum version 1.12)
    Go version:       go1.13.15
    Git commit:       b0f5bc3
    Built:            Wed Jun  2 11:54:50 2021
    OS/Arch:          linux/amd64
    Experimental:     false
    containerd:
    Version:          1.4.8
    GitCommit:        7eba5930496d9bbe375fdf71603e610ad737d2b2
    runc:
    Version:          1.0.0
    GitCommit:        v1.0.0-0-g84113ee
    docker-init:
    Version:          0.19.0
    GitCommit:        de40ad0

2. Run a Nginx container.

    $ docker run -d \
    --name nginx\
    -p 8080:80\
    nginx

    $ docker ps
    CONTAINER ID   IMAGE     COMMAND                  CREATED              STATUS              PORTS                                   NAMES
    4810764994ea   nginx     "/docker-entrypoint.…"   About a minute ago   Up About a minute   0.0.0.0:8080->80/tcp, :::8080->80/tcp   nginx

    $ docker inspect 4810764994ea | grep "IPAddress"
                "SecondaryIPAddresses": null,
                "IPAddress": "172.17.0.2",
                        "IPAddress": "172.17.0.2",

    $ ip a
    1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
        link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
        inet 127.0.0.1/8 scope host lo
        valid_lft forever preferred_lft forever
        inet6 ::1/128 scope host
        valid_lft forever preferred_lft forever
    2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9001 qdisc fq_codel state UP group default qlen 1000
        link/ether 06:6d:9c:00:30:cf brd ff:ff:ff:ff:ff:ff
        inet 172.31.21.51/20 brd 172.31.31.255 scope global dynamic eth0
        valid_lft 3195sec preferred_lft 3195sec
        inet6 fe80::46d:9cff:fe00:30cf/64 scope link
        valid_lft forever preferred_lft forever
    3: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
        link/ether 02:42:fa:a5:24:4c brd ff:ff:ff:ff:ff:ff
        inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
        valid_lft forever preferred_lft forever
        inet6 fe80::42:faff:fea5:244c/64 scope link
        valid_lft forever preferred_lft forever
    5: vethaba889b@if4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP group default
        link/ether a2:5f:fc:b2:f5:11 brd ff:ff:ff:ff:ff:ff link-netnsid 0
        inet6 fe80::a05f:fcff:feb2:f511/64 scope link
        valid_lft forever preferred_lft forever

3. Capture the packets on the sever side, which is running Nginx container.

    $ sudo tcpdump -i any -w lab-nginx.pcap
    tcpdump: listening on any, link-type LINUX_SLL (Linux cooked v1), capture size 262144 bytes
    ^C139 packets captured
    142 packets received by filter
    0 packets dropped by kernel

4. On client side 34.243.235.127(eth0: 172.31.15.47), request HTTP via curl command 3 times.

sever and client are in the same subnet(VPC).
34.243.235.127(eth0: 172.31.15.47) <-> server 54.155.144.125(eth0: 172.31.21.51)

    $ curl 54.155.144.125:8080

If you want to analyze the pcap file, pleaes download the [file](https://drive.google.com/file/d/17yu64m8MjxfApus31c-WhMY6k3Ibs3Ig/view?usp=sharing).

References:
1. https://docs.docker.com/engine/install/ubuntu/