From: Alexey Kodanev alexey.kodanev@oracle.com
[ Upstream commit 53c81e95df1793933f87748d36070a721f6cb287 ]
LTP/udp6_ipsec_vti tests fail when sending large UDP datagrams over ip6_vti that require fragmentation and the underlying device has an MTU smaller than 1500 plus some extra space for headers. This happens because ip6_vti, by default, 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().
In case the lower device has larger MTU size, e.g. 9000, ip6_vti works but not using the possible maximum size, output packets have 1500 limit.
The above cases require manual MTU setup after ip6_vti creation. However ip_vti already updates MTU based on lower device with ip_tunnel_bind_dev().
Here is the example when the lower 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
Reported-by: Petr Vorel pvorel@suse.cz Signed-off-by: Alexey Kodanev alexey.kodanev@oracle.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- net/ipv6/ip6_vti.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c index bcdc2d557de1..413f01be0c9b 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 +639,25 @@ 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); }
/**