LTP/udp6_ipsec_vti tests fail when sending large UDP datagrams that
require fragmentation and the underlying device has MTU <= 1500. This
happens because ip6_vti sets mtu to ETH_DATA_LEN and not updating it
depending on a destination address or link parameter.
Further attempts to send UDP packets may succeed because pmtu gets
updated on ICMPV6_PKT_TOOBIG in vti6_err().
Here is the example when the output device MTU is set to 9000:
# ip a sh ltp_ns_veth2
ltp_ns_veth2@if7: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 ...
inet 10.0.0.2/24 scope global ltp_ns_veth2
inet6 fd00::2/64 scope global
# ip li add vti6 type vti6 local fd00::2 remote fd00::1
# ip li show vti6
vti6@NONE: <POINTOPOINT,NOARP> mtu 1500 ...
link/tunnel6 fd00::2 peer fd00::1
After the patch:
# ip li add vti6 type vti6 local fd00::2 remote fd00::1
# ip li show vti6
vti6@NONE: <POINTOPOINT,NOARP> mtu 8832 ...
link/tunnel6 fd00::2 peer fd00::1
Regarding ip_vti, it already tunes MTU with ip_tunnel_bind_dev().
Reported-by: Petr Vorel <pvo...@suse.cz>
Signed-off-by: Alexey Kodanev <alexey.koda...@oracle.com>
Acked-by: Shannon Nelson <shannon.nel...@oracle.com>
---
v3: * fix style issue with curly braces around single-statement if block
v2: * cleanup commit message issues (thanks to Shannon)
* handle the case when we don't have route but have device parameter
* cast new MTU to int and then check the maximum (tdev->mtu can be
less than dev->hard_header_len)
net/ipv6/ip6_vti.c | 21 +++++++++++++++++++++
1 files changed, 21 insertions(+), 0 deletions(-)
diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index dbb74f3..5404443 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -626,6 +626,7 @@ static void vti6_link_config(struct ip6_tnl *t)
{
struct net_device *dev = t->dev;
struct __ip6_tnl_parm *p = &t->parms;
+ struct net_device *tdev = NULL;
memcpy(dev->dev_addr, &p->laddr, sizeof(struct in6_addr));
memcpy(dev->broadcast, &p->raddr, sizeof(struct in6_addr));
@@ -638,6 +639,26 @@ static void vti6_link_config(struct ip6_tnl *t)
dev->flags |= IFF_POINTOPOINT;
else
dev->flags &= ~IFF_POINTOPOINT;
+
+ if (p->flags & IP6_TNL_F_CAP_XMIT) {
+ int strict = (ipv6_addr_type(&p->raddr) &
+ (IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL));
+
+ struct rt6_info *rt = rt6_lookup(t->net,
+ &p->raddr, &p->laddr,
+ p->link, strict);
+
+ if (rt)
+ tdev = rt->dst.dev;
+ ip6_rt_put(rt);
+ }
+
+ if (!tdev && p->link)
+ tdev = __dev_get_by_index(t->net, p->link);
+
+ if (tdev)
+ dev->mtu = max_t(int, tdev->mtu - dev->hard_header_len,
+ IPV6_MIN_MTU);
}
/**
--
1.7.1
