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datapath: Consider tunnels to have no MTU, fixing jumbo frame support.

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Until now, tunnel vports have had a specific MTU, in the same way that
ordinary network devices have an MTU, but treating them this way does not
always make sense.  For example, consider a datapath that has three ports:
the local port, a GRE tunnel to another host, and a physical port.  If
the physical port is configured with a jumbo MTU, it should be possible to
send jumbo packets across the tunnel: the tunnel can do fragmentation or
the physical port traversed by the tunnel might have a jumbo MTU.

However, until now, tunnels always had a 1500-byte MTU by default.  It
could be adjusted using ODP_VPORT_MTU_SET, but nothing actually did this.
One alternative would be to make ovs-vswitchd able to set the vport's MTU.
This commit, however, takes a different approach, of dropping the concept
of MTU entirely for tunnel vports.  This also solves the problem described
above, without making any additional work for anyone.

I tested that, without this change, I could not send 1600-byte "pings"
between two machines whose NICs had 2000-byte MTUs that were connected to
vswitches that were in turn connected over GRE tunnels with the default
1500-byte MTU.  With this change, it worked OK, regardless of the MTU of
the network traversed by the GRE tunnel.

This patch also makes "patch" ports MTU-less.

It might make sense to remove vport_set_mtu() and the associated callback
now, since ordinary network devices are the only vports that support it
now.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Suggested-by: Jesse Gross <jesse@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>
Bug #3728.
This commit is contained in:
Ben Pfaff
2011-02-01 11:32:06 -08:00
parent bfa68a2b1f
commit f915f1a8ca
17 changed files with 48 additions and 82 deletions
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13
lib/netdev-linux.c
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@@ -2365,6 +2365,11 @@ htb_setup_class__(struct netdev *netdev, unsigned int handle,
int mtu;
netdev_get_mtu(netdev, &mtu);
if (mtu == INT_MAX) {
VLOG_WARN_RL(&rl, "cannot set up HTB on device %s that lacks MTU",
netdev_get_name(netdev));
return EINVAL;
}
memset(&opt, 0, sizeof opt);
tc_fill_rate(&opt.rate, class->min_rate, mtu);
@@ -2484,6 +2489,13 @@ htb_parse_class_details__(struct netdev *netdev,
const char *priority_s = shash_find_data(details, "priority");
int mtu;
netdev_get_mtu(netdev, &mtu);
if (mtu == INT_MAX) {
VLOG_WARN_RL(&rl, "cannot parse HTB class on device %s that lacks MTU",
netdev_get_name(netdev));
return EINVAL;
}
/* min-rate. Don't allow a min-rate below 1500 bytes/s. */
if (!min_rate_s) {
/* min-rate is required. */
@@ -2509,7 +2521,6 @@ htb_parse_class_details__(struct netdev *netdev,
* doesn't include the Ethernet header, we need to add at least 14 (18?) to
* the MTU. We actually add 64, instead of 14, as a guard against
* additional headers get tacked on somewhere that we're not aware of. */
netdev_get_mtu(netdev, &mtu);
hc->burst = burst_s ? strtoull(burst_s, NULL, 10) / 8 : 0;
hc->burst = MAX(hc->burst, mtu + 64);