Attachment 180307 Details for Bug 188990 – [PATCH] dhclient: skip UDP checksum check when running in a Xen VM

[patch] [PATCH] dhclient: skip UDP checksum check when running in a Xen VM

0001-dhclient-skip-UDP-checksum-check-when-running-in-a-X.patch (text/plain), 2.86 KB, created by Bhavesh Davda on 2017-02-26 01:04:23 UTC

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Creator: Bhavesh Davda

Created: 2017-02-26 01:04:23 UTC

Size: 2.86 KB

patch

obsolete

>From 848f31f6485744ae11fe531ac2c79659d657a6d0 Mon Sep 17 00:00:00 2001
>From: bhavesh.davda <bhavesh.davda@oracle.com>
>Date: Sat, 25 Feb 2017 15:36:06 -0800
>Subject: [PATCH] dhclient: skip UDP checksum check when running in a Xen VM
>
>The Xen PV network interface offloads checksum validation on receive and
>checksum computation on transmit, so the UDP checksum in the packet may appear
>to be incorrect. This leads to false negatives and packet drops when receiving
>DHCP packets from a DHCP server running in the Xen dom-0.
>
>Check if dhclient is running in a Xen VM using the 'kern.vm_guest' sysctl and
>skip UDP checksum validation if it is.
>
>Signed-off-by: Bhavesh Davda <bhavesh.davda@oracle.com>
>---
> sbin/dhclient/dhclient.c |   12 ++++++++++++
> sbin/dhclient/packet.c   |    4 +++-
> 2 files changed, 15 insertions(+), 1 deletions(-)
>
>diff --git a/sbin/dhclient/dhclient.c b/sbin/dhclient/dhclient.c
>index d20585d..646e8a3 100644
>--- a/sbin/dhclient/dhclient.c
>+++ b/sbin/dhclient/dhclient.c
>@@ -61,6 +61,7 @@ __FBSDID("$FreeBSD$");
> 
> #include <sys/capsicum.h>
> #include <sys/endian.h>
>+#include <sys/sysctl.h>
> 
> #include <net80211/ieee80211_freebsd.h>
> 
>@@ -96,6 +97,8 @@ int nullfd = -1;
> 
> char hostname[_POSIX_HOST_NAME_MAX + 1];
> 
>+int is_xen_guest = -1;
>+
> struct iaddr iaddr_broadcast = { 4, { 255, 255, 255, 255 } };
> struct in_addr inaddr_any, inaddr_broadcast;
> 
>@@ -351,6 +354,8 @@ main(int argc, char *argv[])
> 	struct passwd		*pw;
> 	pid_t			 otherpid;
> 	cap_rights_t		 rights;
>+	char			 vm_guest[16];
>+	size_t			 sysctl_len = sizeof(vm_guest);
> 
> 	/* Initially, log errors to stderr as well as to syslogd. */
> 	openlog(__progname, LOG_PID | LOG_NDELAY, DHCPD_LOG_FACILITY);
>@@ -462,6 +467,13 @@ main(int argc, char *argv[])
> 	if (gethostname(hostname, sizeof(hostname)) < 0)
> 		hostname[0] = '\0';
> 
>+	/*
>+	 * Check if running in a Xen VM before entering capability mode.
>+	 */
>+	if (sysctlbyname("kern.vm_guest", vm_guest, &sysctl_len, NULL, 0) == 0)
>+		if (strcasecmp(vm_guest, "xen") == 0)
>+			is_xen_guest = 1;
>+
> 	priv_script_init("PREINIT", NULL);
> 	if (ifi->client->alias)
> 		priv_script_write_params("alias_", ifi->client->alias);
>diff --git a/sbin/dhclient/packet.c b/sbin/dhclient/packet.c
>index 859f48b..e691ca5 100644
>--- a/sbin/dhclient/packet.c
>+++ b/sbin/dhclient/packet.c
>@@ -55,6 +55,8 @@ __FBSDID("$FreeBSD$");
> u_int32_t	checksum(unsigned char *, unsigned, u_int32_t);
> u_int32_t	wrapsum(u_int32_t);
> 
>+extern int	is_xen_guest;
>+
> u_int32_t
> checksum(unsigned char *buf, unsigned nbytes, u_int32_t sum)
> {
>@@ -231,7 +233,7 @@ decode_udp_ip_header(unsigned char *buf, int bufix, struct sockaddr_in *from,
> 	    IPPROTO_UDP + (u_int32_t)ntohs(udp->uh_ulen)))));
> 
> 	udp_packets_seen++;
>-	if (usum && usum != sum) {
>+	if (usum && usum != sum && is_xen_guest != 1) {
> 		udp_packets_bad_checksum++;
> 		if (udp_packets_seen > 4 &&
> 		    (udp_packets_seen / udp_packets_bad_checksum) < 2) {
>-- 
>1.7.1
>

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