Ensure that user-specified HOSTNAME is honored

When adding the HOSTNAME environment variable, only do so if it
is not already present in the spec. If it is already present, it
was likely added by the user, and we should honor their requested
value.

Fixes #8886

Signed-off-by: Matthew Heon <mheon@redhat.com>

libpod/container_internal_linux.go

@@ -529,14 +529,37 @@ func (c *Container) generateSpec(ctx context.Context) (*spec.Spec, error) {
 		}
 	}
 
+	// Hostname handling:
+	// If we have a UTS namespace, set Hostname in the OCI spec.
+	// Set the HOSTNAME environment variable unless explicitly overridden by
+	// the user (already present in OCI spec). If we don't have a UTS ns,
+	// set it to the host's hostname instead.
+	hostname := c.Hostname()
+	foundUTS := false
 	for _, i := range c.config.Spec.Linux.Namespaces {
 		if i.Type == spec.UTSNamespace && i.Path == "" {
-			hostname := c.Hostname()
+			foundUTS = true
 			g.SetHostname(hostname)
-			g.AddProcessEnv("HOSTNAME", hostname)
 			break
 		}
 	}
+	if !foundUTS {
+		tmpHostname, err := os.Hostname()
+		if err != nil {
+			return nil, err
+		}
+		hostname = tmpHostname
+	}
+	needEnv := true
+	for _, checkEnv := range g.Config.Process.Env {
+		if strings.SplitN(checkEnv, "=", 2)[0] == "HOSTNAME" {
+			needEnv = false
+			break
+		}
+	}
+	if needEnv {
+		g.AddProcessEnv("HOSTNAME", hostname)
+	}
 
 	if c.config.UTSNsCtr != "" {
 		if err := c.addNamespaceContainer(&g, UTSNS, c.config.UTSNsCtr, spec.UTSNamespace); err != nil {

pkg/specgen/generate/namespaces.go

@@ -364,7 +364,9 @@ func specConfigureNamespaces(s *specgen.SpecGenerator, g *generate.Generator, rt
 		// namespaces?
 		g.SetHostname(hostname)
 	}
+	if _, ok := s.Env["HOSTNAME"]; !ok && s.Hostname != "" {
 		g.AddProcessEnv("HOSTNAME", hostname)
+	}
 
 	// User
 	switch s.UserNS.NSMode {

test/e2e/run_test.go

@@ -1415,4 +1415,12 @@ WORKDIR /madethis`
 		Expect(session.ExitCode()).To(Equal(0))
 		Expect(session.ErrorToString()).To(ContainSubstring("Trying to pull"))
 	})
+
+	It("podman run container with hostname and hostname environment variable", func() {
+		hostnameEnv := "test123"
+		session := podmanTest.Podman([]string{"run", "--hostname", "testctr", "--env", fmt.Sprintf("HOSTNAME=%s", hostnameEnv), ALPINE, "printenv", "HOSTNAME"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		Expect(session.OutputToString()).To(ContainSubstring(hostnameEnv))
+	})
 })