From 3c1a73d3700056b084eb017ebe02dbbca7c3b064 Mon Sep 17 00:00:00 2001
From: Denton Gentry <dgentry@tailscale.com>
Date: Sun, 25 Apr 2021 12:38:37 -0700
Subject: [PATCH] hostinfo: detect AWS Lambda as a container.

AWS Lambda uses Docker containers but does not
have the string "docker" in its /proc/1/cgroup.
Infer AWS Lambda via the environment variables
it sets.

Signed-off-by: Denton Gentry <dgentry@tailscale.com>
---
 control/controlclient/hostinfo_linux.go | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/control/controlclient/hostinfo_linux.go b/control/controlclient/hostinfo_linux.go
index e79eaaa89..364e1098b 100644
--- a/control/controlclient/hostinfo_linux.go
+++ b/control/controlclient/hostinfo_linux.go
@@ -62,6 +62,9 @@ func osVersionLinux() string {
 	if inKnative() {
 		attrBuf.WriteString("; env=kn")
 	}
+	if inAwsLambda() {
+		attrBuf.WriteString("; env=lm")
+	}
 	attr := attrBuf.String()
 
 	id := m["ID"]
@@ -121,3 +124,14 @@ func inKnative() bool {
 	}
 	return false
 }
+
+func inAwsLambda() bool {
+	// https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html
+	if os.Getenv("AWS_LAMBDA_FUNCTION_NAME") != "" &&
+		os.Getenv("AWS_LAMBDA_FUNCTION_VERSION") != "" &&
+		os.Getenv("AWS_LAMBDA_INITIALIZATION_TYPE") != "" &&
+		os.Getenv("AWS_LAMBDA_RUNTIME_API") != "" {
+		return true
+	}
+	return false
+}