The nr_conns variable in the sync message header is only eight bits wide
and will overflow on interfaces with a large MTU. As a result the backup
won't parse all connections contained in the sync buffer. On regular
ethernet with an MTU of 1500 this isn't a problem, because we can't
overflow the value, but consider jumbo frames being used on a cross-over
connection between both directors.
We now restrict the size of the sync buffer, so that we never put more
than 255 connections into a single sync buffer.
Signed-off-by: Sven Wegener <sven.wegener@xxxxxxxxxxx>
---
net/ipv4/ipvs/ip_vs_sync.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/ipvs/ip_vs_sync.c b/net/ipv4/ipvs/ip_vs_sync.c
index 28237a5..de5e7e1 100644
--- a/net/ipv4/ipvs/ip_vs_sync.c
+++ b/net/ipv4/ipvs/ip_vs_sync.c
@@ -30,6 +30,7 @@
#include <linux/err.h>
#include <linux/kthread.h>
#include <linux/wait.h>
+#include <linux/kernel.h>
#include <net/ip.h>
#include <net/sock.h>
@@ -99,6 +100,7 @@ struct ip_vs_sync_thread_data {
*/
#define SYNC_MESG_HEADER_LEN 4
+#define MAX_CONNS_PER_SYNCBUFF 255 /* nr_conns in ip_vs_sync_mesg is 8 bit */
struct ip_vs_sync_mesg {
__u8 nr_conns;
@@ -516,8 +518,8 @@ static int set_sync_mesg_maxlen(int sync_state)
num = (dev->mtu - sizeof(struct iphdr) -
sizeof(struct udphdr) -
SYNC_MESG_HEADER_LEN - 20) / SIMPLE_CONN_SIZE;
- sync_send_mesg_maxlen =
- SYNC_MESG_HEADER_LEN + SIMPLE_CONN_SIZE * num;
+ sync_send_mesg_maxlen = SYNC_MESG_HEADER_LEN +
+ SIMPLE_CONN_SIZE * min(num, MAX_CONNS_PER_SYNCBUFF);
IP_VS_DBG(7, "setting the maximum length of sync sending "
"message %d.\n", sync_send_mesg_maxlen);
} else if (sync_state == IP_VS_STATE_BACKUP) {
--
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