feat: add tests for special IP in --add-host flag (#29)

Signed-off-by: Ziwen Ning <ningziwe@amazon.com>

Issue #, if available:
runfinch/finch#209

*Description of changes:*
Start a server in host and try to curl it from container with
`--add-host test-host:host-gateway`

*Testing done:*
`make run` with the change runfinch/finch#216



- [ X ] I've reviewed the guidance in CONTRIBUTING.md


#### License Acceptance

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

Signed-off-by: Ziwen Ning <ningziwe@amazon.com>

run/run_test.go

@@ -38,13 +38,14 @@ func TestRun(t *testing.T) {
 	}, func() {})
 
 	const description = "Finch Shared E2E Tests"
+	const defaultHostGatewayIP = "192.168.5.2"
 	ginkgo.Describe(description, func() {
 		// Every test should be listed here.
 		// TODO: add tests for "system prune" and "network prune" after upgrading nerdctl to v0.23
 		tests.Pull(o)
 		tests.Rm(o)
 		tests.Rmi(o)
-		tests.Run(&tests.RunOption{BaseOpt: o, CGMode: tests.Unified})
+		tests.Run(&tests.RunOption{BaseOpt: o, CGMode: tests.Unified, DefaultHostGatewayIP: defaultHostGatewayIP})
 		tests.Start(o)
 		tests.Stop(o)
 		tests.Cp(o)

tests/run.go

@@ -4,8 +4,11 @@
 package tests
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
+	"io"
+	"net/http"
 	"os"
 	"path/filepath"
 	"strings"
@@ -27,6 +30,8 @@ type RunOption struct {
 	BaseOpt *option.Option
 	// CGMode is the cgroup mode that the host uses.
 	CGMode CGMode
+	// DefaultHostGatewayIP is the IP that the test subject will resolve special IP `host-gateway` to.
+	DefaultHostGatewayIP string
 }
 
 // Run tests running a container image.
@@ -327,6 +332,24 @@ func Run(o *RunOption) {
 				gomega.Expect(mapping).Should(gomega.ContainSubstring("test-host"))
 			})
 
+			ginkgo.It("should add a custom host-to-IP mapping with --add-host flag with special IP", func() {
+				response := "This is the expected response for --add-host special IP test."
+				http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+					io.WriteString(w, response) //nolint:errcheck,gosec // Function call in server handler for testing only.
+				})
+				hostPort := fnet.GetFreePort()
+				s := http.Server{Addr: fmt.Sprintf(":%d", hostPort), Handler: nil, ReadTimeout: 30 * time.Second}
+				go s.ListenAndServe() //nolint:errcheck // Asynchronously starting server for testing only.
+				ginkgo.DeferCleanup(s.Shutdown, context.Background())
+				command.Run(o.BaseOpt, "run", "-d", "--name", testContainerName, "--add-host", "test-host:host-gateway",
+					amazonLinux2Image, "sleep", "infinity")
+				mapping := command.StdoutStr(o.BaseOpt, "exec", testContainerName, "cat", "/etc/hosts")
+				gomega.Expect(mapping).Should(gomega.ContainSubstring(o.DefaultHostGatewayIP))
+				gomega.Expect(mapping).Should(gomega.ContainSubstring("test-host"))
+				gomega.Expect(command.StdoutStr(o.BaseOpt, "exec", testContainerName, "curl",
+					fmt.Sprintf("test-host:%d", hostPort))).Should(gomega.Equal(response))
+			})
+
 			for _, publish := range []string{"-p", "--publish"} {
 				publish := publish
 				ginkgo.It(fmt.Sprintf("port of the container should be published to the host port with %s flag", publish), func() {

tests/tests.go

@@ -27,6 +27,7 @@ import (
 const (
 	alpineImage              = "public.ecr.aws/docker/library/alpine:latest"
 	olderAlpineImage         = "public.ecr.aws/docker/library/alpine:3.13"
+	amazonLinux2Image        = "public.ecr.aws/amazonlinux/amazonlinux:2"
 	testImageName            = "test:tag"
 	nonexistentImageName     = "ne-repo:ne-tag"
 	nonexistentContainerName = "ne-ctr"