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Handle gratuitous ARP requests and replies in tnl_arp_snoop()

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Problem:
========
In user-space tunneling implementation, tnl_arp_snoop() snoops only ARP
*reply* packets to resolve tunnel nexthop IP addresses to MAC addresses.
Normally the ARP requests are periodically sent by the local host IP stack,
so that the ARP cache in OVS is refreshed and entries do not time out.
However, if the remote tunnel nexthop is a VRRP IP, and the gateway
periodically sends gratuitous ARP *requests* to announce itself,
tnl_arp_snoop() treats them as INVALID. Consequently, the ARP cache in OVS
expires after 10 minutes, which results in dropping of the next packet(s)
until a new ARP request is responded to.

Fix:
====
Enhance the tunnel neighbor resolution logic in OVS to not only snoop on
ARP replies but also on gratuitous ARP requests.

Signed-off-by: Jan Scheurich <jan.scheurich@ericsson.com>
From: Manohar K C <manohar.krishnappa.chidambaraswamy@ericsson.com>
CC: Jan Scheurich <jan.scheurich@ericsson.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
This commit is contained in:
Manohar Krishnappa Chidambaraswamy
2018-04-05 12:20:27 +00:00
committed by Ben Pfaff
parent 484f7dbdaa
commit ba07cf222a
2 changed files with 20 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
lib/flow.h
View File

@@ -1118,6 +1118,22 @@ static inline bool is_nd(const struct flow *flow,
return false;
}
static inline bool is_arp(const struct flow *flow)
{
return (flow->dl_type == htons(ETH_TYPE_ARP));
}
static inline bool is_garp(const struct flow *flow,
struct flow_wildcards *wc)
{
if (is_arp(flow)) {
return (FLOW_WC_GET_AND_MASK_WC(flow, wc, nw_src) ==
FLOW_WC_GET_AND_MASK_WC(flow, wc, nw_dst));
}
return false;
}
static inline bool is_igmp(const struct flow *flow, struct flow_wildcards *wc)
{
if (get_dl_type(flow) == htons(ETH_TYPE_IP)) {

6
lib/tnl-neigh-cache.c
View File

@@ -151,8 +151,10 @@ static int
tnl_arp_snoop(const struct flow *flow, struct flow_wildcards *wc,
const char name[IFNAMSIZ])
{
if (flow->dl_type != htons(ETH_TYPE_ARP)
|| FLOW_WC_GET_AND_MASK_WC(flow, wc, nw_proto) != ARP_OP_REPLY
/* Snoop normal ARP replies and gratuitous ARP requests/replies only */
if (!is_arp(flow)
|| (!is_garp(flow, wc) &&
FLOW_WC_GET_AND_MASK_WC(flow, wc, nw_proto) != ARP_OP_REPLY)
|| eth_addr_is_zero(FLOW_WC_GET_AND_MASK_WC(flow, wc, arp_sha))) {
return EINVAL;
}