From 0b1258b44cb7412e2c8a01640aeeef25a7c36080 Mon Sep 17 00:00:00 2001
From: Joachim Wiberg <troglobit@gmail.com>
Date: Sun, 27 Feb 2022 23:52:18 +0100
Subject: [PATCH] Add very basic in_container() function, from sysklogd project

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
---
 src/helpers.c | 33 +++++++++++++++++++++++++++++++++
 src/helpers.h |  1 +
 2 files changed, 34 insertions(+)

diff --git a/src/helpers.c b/src/helpers.c
index fd352f8d..a06cd1cc 100644
--- a/src/helpers.c
+++ b/src/helpers.c
@@ -522,6 +522,39 @@ done:
 	}
 }
 
+/*
+ * Very basic, and incomplete, check if we're running in a container.
+ */
+int in_container(void)
+{
+	const char *files[] = {
+		"/run/.containerenv",
+		"/.dockerenv"
+	};
+	const char *containers[] = {
+		"lxc",
+		"docker",
+		"kubepod"
+	};
+	size_t i;
+	char *c;
+
+	c = getenv("container");
+	if (c) {
+		for (i = 0; i < NELEMS(containers); i++) {
+			if (!strcmp(containers[i], c))
+				return 1;
+		}
+	}
+
+	for (i = 0; i < NELEMS(files); i++) {
+		if (!access(files[i], F_OK))
+			return 1;
+	}
+
+	return 0;
+}
+
 #ifndef HAVE_GETFSENT
 static lfile_t *fstab = NULL;
 
diff --git a/src/helpers.h b/src/helpers.h
index 07b70d02..839a2952 100644
--- a/src/helpers.h
+++ b/src/helpers.h
@@ -93,6 +93,7 @@ int     mksubsys        (const char *dir, mode_t mode, char *user, char *group);
 
 void    set_hostname    (char **hostname);
 void    networking      (int updown);
+int     in_container    (void);
 
 int     complete        (char *cmd, int pid);
 int     run             (char *cmd);