From e3892606908bf60c9532cf10b0c4e46868806fe1 Mon Sep 17 00:00:00 2001
From: Mikael Magnusson <mikma@users.sourceforge.net>
Date: Thu, 2 Sep 2021 01:10:43 +0200
Subject: uhttpd: add SO_BINDTODEVICE support

Add command line option "-b <interface>" which binds the ports
(and addresses) in the following "-p" and "-s" options to the specified
network interface with SO_BINDTODEVICE.

Using SO_BINDTODEVICE means uhttpd will only accept incoming traffic from
the specified network interface.

Signed-off-by: Mikael Magnusson <mikma@users.sourceforge.net>
---
 listen.c |  7 ++++++-
 main.c   | 18 ++++++++++++++----
 uhttpd.h |  2 +-
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/listen.c b/listen.c
index 2a54888..908127a 100644
--- a/listen.c
+++ b/listen.c
@@ -128,7 +128,7 @@ void uh_setup_listeners(void)
 	}
 }
 
-int uh_socket_bind(const char *host, const char *port, bool tls)
+int uh_socket_bind(const char *host, const char *port, const char *device, bool tls)
 {
 	int sock = -1;
 	int yes = 1;
@@ -169,6 +169,11 @@ int uh_socket_bind(const char *host, const char *port, bool tls)
 			goto error;
 		}
 
+		if (device && setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, device, strlen(device)) < 0) {
+			perror("setsockopt()");
+			goto error;
+		}
+
 		/* bind */
 		if (bind(sock, p->ai_addr, p->ai_addrlen) < 0) {
 			perror("bind()");
diff --git a/main.c b/main.c
index 73e3d42..dd2d3d0 100644
--- a/main.c
+++ b/main.c
@@ -103,7 +103,7 @@ static void uh_config_parse(void)
 	fclose(c);
 }
 
-static int add_listener_arg(char *arg, bool tls)
+static int add_listener_arg(char *arg, const char *device, bool tls)
 {
 	char *host = NULL;
 	char *port = arg;
@@ -125,7 +125,7 @@ static int add_listener_arg(char *arg, bool tls)
 		}
 	}
 
-	return uh_socket_bind(host, port, tls);
+	return uh_socket_bind(host, port, device, tls);
 }
 
 static int usage(const char *name)
@@ -134,6 +134,8 @@ static int usage(const char *name)
 		"Usage: %s -p [addr:]port -h docroot\n"
 		"	-f              Do not fork to background\n"
 		"	-c file         Configuration file, default is '/etc/httpd.conf'\n"
+		"	-b interface    Bind subsequent ports (and addresses) to specified"
+		"	                network interface with SO_BINDTODEVICE\n"
 		"	-p [addr:]port  Bind to specified address and port, multiple allowed\n"
 #ifdef HAVE_TLS
 		"	-s [addr:]port  Like -p but provide HTTPS on this port\n"
@@ -256,6 +258,7 @@ int main(int argc, char **argv)
 #ifdef HAVE_LUA
 	const char *lua_prefix = NULL, *lua_handler = NULL;
 #endif
+	char *device = NULL;
 
 	BUILD_BUG_ON(sizeof(uh_buf) < PATH_MAX);
 
@@ -263,7 +266,7 @@ int main(int argc, char **argv)
 	init_defaults_pre();
 	signal(SIGPIPE, SIG_IGN);
 
-	while ((ch = getopt(argc, argv, "A:aC:c:Dd:E:e:fh:H:I:i:K:k:L:l:m:N:n:P:p:qRr:Ss:T:t:U:u:Xx:y:")) != -1) {
+	while ((ch = getopt(argc, argv, "A:ab:C:c:Dd:E:e:fh:H:I:i:K:k:L:l:m:N:n:P:p:qRr:Ss:T:t:U:u:Xx:y:")) != -1) {
 		switch(ch) {
 #ifdef HAVE_TLS
 		case 'C':
@@ -282,6 +285,13 @@ int main(int argc, char **argv)
 			conf.tls_redirect = 1;
 			break;
 
+		case 'b':
+			if (optarg[0] == '\0')
+				device = NULL;
+			else
+				device = optarg;
+			break;
+
 		case 's':
 			n_tls++;
 			/* fall through */
@@ -297,7 +307,7 @@ int main(int argc, char **argv)
 #endif
 		case 'p':
 			optarg = strdup(optarg);
-			bound += add_listener_arg(optarg, (ch == 's'));
+			bound += add_listener_arg(optarg, device, (ch == 's'));
 			break;
 
 		case 'h':
diff --git a/uhttpd.h b/uhttpd.h
index e61e176..77273a7 100644
--- a/uhttpd.h
+++ b/uhttpd.h
@@ -289,7 +289,7 @@ bool uh_accept_client(int fd, bool tls);
 
 void uh_unblock_listeners(void);
 void uh_setup_listeners(void);
-int uh_socket_bind(const char *host, const char *port, bool tls);
+int uh_socket_bind(const char *host, const char *port, const char *device, bool tls);
 
 int uh_first_tls_port(int family);
 
-- 
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