testing: add offline testing container for CI

This patch adds the necessary code for building a container that can be
used for our CI functional and fullstack testing needs. The only
requirement for building is a working docker engine and the OS to have
access to a packaging mirror (which CI is supposed to have even when
internet connectivity is limited).

In order to build, simply move to 'contrib/testing/container' and run:

    ./build.sh

To try it out locally, just do:

    docker build -t kuryr/testing_container .
    docker run --rm -p 8000:8000 kuryr/testing_container

And from another terminal:

    curl 0:8000

Change-Id: Id94ad2d7567f9e5d60fce25d29c8c3d4a391aabc
Signed-off-by: Antoni Segura Puimedon <antonisp@celebdor.com>

contrib/testing/container/Dockerfile

@@ -0,0 +1,3 @@
+FROM scratch
+ADD kuryr_testing_rootfs.tar.gz /
+CMD ["/usr/bin/kuryr_hostname"]

contrib/testing/container/build.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+
+set -o errexit
+
+
+function install_busybox {
+    if [[ -x $(command -v apt-get 2> /dev/null) ]]; then
+        sudo apt-get update
+        sudo apt-get install -y busybox-static gcc
+    elif [[ -x $(command -v dnf 2> /dev/null) ]]; then
+        sudo dnf install -y busybox gcc
+    elif [[ -x $(command -v yum 2> /dev/null) ]]; then
+        sudo yum install -y busybox gcc
+    elif [[ -x $(command -v pacman 2> /dev/null) ]]; then
+        sudo pacman -S --noconfirm busybox gcc
+    else
+        echo "unknown distro" 1>2
+        exit 1
+    fi
+    return 0
+}
+
+function make_root {
+    local root_dir
+    local binary
+
+    root_dir=$(mktemp -d)
+    mkdir -p "${root_dir}/bin" "${root_dir}/usr/bin"
+    binary=$(command -v busybox)
+    cp "$binary" "${root_dir}/bin/busybox"
+    "${root_dir}/bin/busybox" --install "${root_dir}/bin"
+    gcc --static hostname.c -o "${root_dir}/usr/bin/kuryr_hostname"
+    tar -C "$root_dir" -czvf kuryr_testing_rootfs.tar.gz bin usr
+    return 0
+}
+
+function build_container {
+    docker build -t kuryr/test_container .
+}
+
+install_busybox
+make_root
+build_container

contrib/testing/container/hostname.c

@@ -0,0 +1,129 @@
+#define _GNU_SOURCE
+#include <arpa/inet.h>
+#include <err.h>
+#include <errno.h>
+#include <linux/in.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#define MAX_LEN 1024
+#define BACKLOG 10
+#define LISTENING_PORT 8000
+
+volatile sig_atomic_t running = 1;
+volatile sig_atomic_t sig_number;
+
+static void handler(int signo) {
+	sig_number = signo;
+	running = 0;
+}
+
+
+int main() {
+	struct sigaction sa = {
+		.sa_handler = handler,
+		.sa_flags = 0};
+	sigemptyset(&sa.sa_mask);
+
+	if (sigaction(SIGINT, &sa, NULL) == -1) {
+		err(1, "Failed to set SIGINT handler");
+	}
+	if (sigaction(SIGTERM, &sa, NULL) == -1) {
+		err(1, "Failed to set SIGTERM handler");
+	}
+
+	int enable = 1;
+	int result = 1;
+	char hostname[MAX_LEN];
+	int res = gethostname(hostname, MAX_LEN);
+	if (res < 0) {
+		err(1, "Failed to retrieve hostname");
+	}
+
+	char *response;
+	ssize_t responselen;
+	responselen = asprintf(&response, "HTTP/1.1 200 OK\r\n"
+			"Content-Type: text/html; charset=UTF-8\r\n\r\n"
+			"%s\r\n", hostname);
+	if (responselen == -1) {
+		err(1, "Failed to form response");
+	}
+
+	int sock = socket(AF_INET, SOCK_STREAM, 0);
+	if (sock < 0) {
+		perror("Failed to open socket");
+		goto nosocket;
+	}
+
+	res = setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &enable,
+			sizeof(int));
+	if (res < 0) {
+		perror("Failed to set socket options");
+		goto cleanup;
+	}
+
+	struct sockaddr_in srv = {
+		.sin_family = AF_INET,
+		.sin_port = htons(LISTENING_PORT),
+		.sin_addr = { .s_addr = INADDR_ANY}};
+	socklen_t addrlen= sizeof(srv);
+
+	res = bind(sock, (struct sockaddr *) &srv, (socklen_t) sizeof(srv));
+	if (res < 0) {
+		res = close(sock);
+		if (res == -1) {
+			perror("Failed close socket");
+			goto cleanup;
+		}
+		perror("Failed to bind socket");
+		goto cleanup;
+	}
+
+	res = listen(sock, BACKLOG);
+	if (res < 0) {
+		perror("Failed to set socket to listen");
+		goto cleanup;
+	}
+
+	while (running) {
+		struct sockaddr_in cli;
+		int client_fd = accept(sock, (struct sockaddr *) &cli,
+				&addrlen);
+		if (client_fd == -1) {
+			if (running) {
+				perror("failed to accept connection");
+				continue;
+			} else {
+				char *signame = strsignal(sig_number);
+				printf("Received %s. Quitting\n", signame);
+				break;
+			}
+		}
+		fprintf(stderr, "Accepted client connection\n");
+
+		/* Assume we write it all at once */
+		write(client_fd, response, responselen);
+		res = shutdown(client_fd, SHUT_RDWR);
+		if (res == -1) {
+			perror("Failed to shutdown client connection");
+			goto cleanup;
+		}
+		res = close(client_fd);
+		if (res == -1) {
+			perror("Failed to close client connection");
+			goto cleanup;
+		}
+	}
+
+	result = 0;
+cleanup:
+	close(sock);
+nosocket:
+	free(response);
+	return result;
+}