From 48bf6bad1deef63d56444bf2261af22b1704803a Mon Sep 17 00:00:00 2001
From: netblue30 <netblue30@yahoo.com>
Date: Thu, 27 Jul 2017 13:19:05 -0400
Subject: tentative fix for arp cahce pollution -  #1406

---
 src/firejail/arp.c          | 9 ++++++---
 src/firejail/firejail.h     | 2 +-
 src/firejail/network_main.c | 2 +-
 src/firejail/sandbox.c      | 2 +-
 4 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/firejail/arp.c b/src/firejail/arp.c
index 10cfe507f..6d21167f0 100644
--- a/src/firejail/arp.c
+++ b/src/firejail/arp.c
@@ -42,7 +42,10 @@ typedef struct arp_hdr_t {
 
 
 // returns 0 if the address is not in use, -1 otherwise
-int arp_check(const char *dev, uint32_t destaddr, uint32_t srcaddr) {
+int arp_check(const char *dev, uint32_t destaddr) {
+	// RFC 5227 - using a source IP address of 0 for probing
+	uint32_t srcaddr = 0;
+
 	if (strlen(dev) > IFNAMSIZ) {
 		fprintf(stderr, "Error: invalid network device name %s\n", dev);
 		exit(1);
@@ -206,7 +209,7 @@ static uint32_t arp_random(const char *dev, Bridge *br) {
 		return 0;
 
 	// check address
-	uint32_t rv = arp_check(dev, dest, ifip);
+	uint32_t rv = arp_check(dev, dest);
 	if (!rv)
 		return dest;
 	return 0;
@@ -248,7 +251,7 @@ static uint32_t arp_sequential(const char *dev, Bridge *br) {
 			dest++;
 			continue;
 		}
-		uint32_t rv = arp_check(dev, dest, ifip);
+		uint32_t rv = arp_check(dev, dest);
 		if (!rv)
 			return dest;
 		dest++;
diff --git a/src/firejail/firejail.h b/src/firejail/firejail.h
index 6aa29f896..5fd978f51 100644
--- a/src/firejail/firejail.h
+++ b/src/firejail/firejail.h
@@ -447,7 +447,7 @@ int restricted_shell(const char *user);
 
 // arp.c
 // returns 0 if the address is not in use, -1 otherwise
-int arp_check(const char *dev, uint32_t destaddr, uint32_t srcaddr);
+int arp_check(const char *dev, uint32_t destaddr);
 // assign an IP address using arp scanning
 uint32_t arp_assign(const char *dev, Bridge *br);
 
diff --git a/src/firejail/network_main.c b/src/firejail/network_main.c
index 11e27575b..172395146 100644
--- a/src/firejail/network_main.c
+++ b/src/firejail/network_main.c
@@ -98,7 +98,7 @@ void net_configure_sandbox_ip(Bridge *br) {
 			exit(1);
 		}
 		// send an ARP request and check if there is anybody on this IP address
-		if (arp_check(br->dev, br->ipsandbox, br->ip)) {
+		if (arp_check(br->dev, br->ipsandbox)) {
 			fprintf(stderr, "Error: IP address %d.%d.%d.%d is already in use\n", PRINT_IP(br->ipsandbox));
 			exit(1);
 		}
diff --git a/src/firejail/sandbox.c b/src/firejail/sandbox.c
index ea39ed580..8c5c02d41 100644
--- a/src/firejail/sandbox.c
+++ b/src/firejail/sandbox.c
@@ -153,7 +153,7 @@ static void sandbox_if_up(Bridge *br) {
 				exit(1);
 			}
 
-			uint32_t rv = arp_check(dev, br->ipsandbox, br->ip);
+			uint32_t rv = arp_check(dev, br->ipsandbox);
 			if (rv) {
 				fprintf(stderr, "Error: the address %d.%d.%d.%d is already in use.\n", PRINT_IP(br->ipsandbox));
 				exit(1);
-- 
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