From 8f844a66d5d144eeb92870c27171dc8b35788d4f Mon Sep 17 00:00:00 2001
From: Matthew Heon <mheon@redhat.com>
Date: Tue, 5 Jan 2021 11:48:37 -0500
Subject: [PATCH] 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 | 27 +++++++++++++++++++++++++--
 pkg/specgen/generate/namespaces.go |  4 +++-
 test/e2e/run_test.go               |  8 ++++++++
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index 05b149e03f..cefe122099 100644
--- a/libpod/container_internal_linux.go
+++ b/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 {
diff --git a/pkg/specgen/generate/namespaces.go b/pkg/specgen/generate/namespaces.go
index 036c7b7a16..3cd5a3c9c5 100644
--- a/pkg/specgen/generate/namespaces.go
+++ b/pkg/specgen/generate/namespaces.go
@@ -364,7 +364,9 @@ func specConfigureNamespaces(s *specgen.SpecGenerator, g *generate.Generator, rt
 		// namespaces?
 		g.SetHostname(hostname)
 	}
-	g.AddProcessEnv("HOSTNAME", hostname)
+	if _, ok := s.Env["HOSTNAME"]; !ok && s.Hostname != "" {
+		g.AddProcessEnv("HOSTNAME", hostname)
+	}
 
 	// User
 	switch s.UserNS.NSMode {
diff --git a/test/e2e/run_test.go b/test/e2e/run_test.go
index 4888a676b1..92d7d222e4 100644
--- a/test/e2e/run_test.go
+++ b/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))
+	})
 })