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ip6_vti: adjust vti mtu according to mtu of lower device
[ Upstream commit 53c81e95df
]
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 20 additions and 0 deletions
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@ -625,6 +625,7 @@ static void vti6_link_config(struct ip6_tnl *t)
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{
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struct net_device *dev = t->dev;
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struct __ip6_tnl_parm *p = &t->parms;
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struct net_device *tdev = NULL;
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memcpy(dev->dev_addr, &p->laddr, sizeof(struct in6_addr));
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memcpy(dev->broadcast, &p->raddr, sizeof(struct in6_addr));
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@ -637,6 +638,25 @@ static void vti6_link_config(struct ip6_tnl *t)
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dev->flags |= IFF_POINTOPOINT;
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else
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dev->flags &= ~IFF_POINTOPOINT;
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if (p->flags & IP6_TNL_F_CAP_XMIT) {
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int strict = (ipv6_addr_type(&p->raddr) &
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(IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL));
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struct rt6_info *rt = rt6_lookup(t->net,
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&p->raddr, &p->laddr,
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p->link, strict);
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if (rt)
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tdev = rt->dst.dev;
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ip6_rt_put(rt);
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}
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if (!tdev && p->link)
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tdev = __dev_get_by_index(t->net, p->link);
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if (tdev)
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dev->mtu = max_t(int, tdev->mtu - dev->hard_header_len,
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IPV6_MIN_MTU);
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}
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/**
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