* [net] net: ip_tunnel: fix mtu calculation
@ 2021-01-28 3:48 Vadim Fedorenko
2021-01-28 21:48 ` Willem de Bruijn
0 siblings, 1 reply; 3+ messages in thread
From: Vadim Fedorenko @ 2021-01-28 3:48 UTC (permalink / raw)
To: Jakub Kicinski, Cong Wang, Slava Bacherikov; +Cc: Vadim Fedorenko, netdev
dev->hard_header_len for tunnel interface is set only when header_ops
are set too and already contains full overhead of any tunnel encapsulation.
That's why there is not need to use this overhead twice in mtu calc.
Fixes: fdafed459998 ("ip_gre: set dev->hard_header_len and dev->needed_headroom properly")
Reported-by: Slava Bacherikov <mail@slava.cc>
Signed-off-by: Vadim Fedorenko <vfedorenko@novek.ru>
---
net/ipv4/ip_tunnel.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 64594aa..ad78825 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -317,7 +317,7 @@ static int ip_tunnel_bind_dev(struct net_device *dev)
}
dev->needed_headroom = t_hlen + hlen;
- mtu -= (dev->hard_header_len + t_hlen);
+ mtu -= dev->hard_header_len ? : t_hlen;
if (mtu < IPV4_MIN_MTU)
mtu = IPV4_MIN_MTU;
@@ -347,7 +347,7 @@ static struct ip_tunnel *ip_tunnel_create(struct net *net,
nt = netdev_priv(dev);
t_hlen = nt->hlen + sizeof(struct iphdr);
dev->min_mtu = ETH_MIN_MTU;
- dev->max_mtu = IP_MAX_MTU - dev->hard_header_len - t_hlen;
+ dev->max_mtu = IP_MAX_MTU - dev->hard_header_len ? : t_hlen;
ip_tunnel_add(itn, nt);
return nt;
@@ -488,11 +488,11 @@ static int tnl_update_pmtu(struct net_device *dev, struct sk_buff *skb,
int mtu;
tunnel_hlen = md ? tunnel_hlen : tunnel->hlen;
- pkt_size = skb->len - tunnel_hlen - dev->hard_header_len;
+ pkt_size = skb->len - dev->hard_header_len ? : tunnel_hlen;
if (df)
- mtu = dst_mtu(&rt->dst) - dev->hard_header_len
- - sizeof(struct iphdr) - tunnel_hlen;
+ mtu = dst_mtu(&rt->dst) - dev->hard_header_len ? :
+ (sizeof(struct iphdr) + tunnel_hlen);
else
mtu = skb_valid_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu;
@@ -972,7 +972,7 @@ int __ip_tunnel_change_mtu(struct net_device *dev, int new_mtu, bool strict)
{
struct ip_tunnel *tunnel = netdev_priv(dev);
int t_hlen = tunnel->hlen + sizeof(struct iphdr);
- int max_mtu = IP_MAX_MTU - dev->hard_header_len - t_hlen;
+ int max_mtu = IP_MAX_MTU - dev->hard_header_len ? : t_hlen;
if (new_mtu < ETH_MIN_MTU)
return -EINVAL;
@@ -1149,10 +1149,10 @@ int ip_tunnel_newlink(struct net_device *dev, struct nlattr *tb[],
mtu = ip_tunnel_bind_dev(dev);
if (tb[IFLA_MTU]) {
- unsigned int max = IP_MAX_MTU - dev->hard_header_len - nt->hlen;
+ unsigned int max = IP_MAX_MTU - dev->hard_header_len ? :
+ (nt->hlen + sizeof(struct iphdr));
- mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU,
- (unsigned int)(max - sizeof(struct iphdr)));
+ mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU, max);
}
err = dev_set_mtu(dev, mtu);
--
1.8.3.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [net] net: ip_tunnel: fix mtu calculation
2021-01-28 3:48 [net] net: ip_tunnel: fix mtu calculation Vadim Fedorenko
@ 2021-01-28 21:48 ` Willem de Bruijn
2021-01-29 0:56 ` Vadim Fedorenko
0 siblings, 1 reply; 3+ messages in thread
From: Willem de Bruijn @ 2021-01-28 21:48 UTC (permalink / raw)
To: Vadim Fedorenko
Cc: Jakub Kicinski, Cong Wang, Slava Bacherikov, Network Development
On Wed, Jan 27, 2021 at 11:14 PM Vadim Fedorenko <vfedorenko@novek.ru> wrote:
>
> dev->hard_header_len for tunnel interface is set only when header_ops
> are set too and already contains full overhead of any tunnel encapsulation.
> That's why there is not need to use this overhead twice in mtu calc.
>
> Fixes: fdafed459998 ("ip_gre: set dev->hard_header_len and dev->needed_headroom properly")
> Reported-by: Slava Bacherikov <mail@slava.cc>
> Signed-off-by: Vadim Fedorenko <vfedorenko@novek.ru>
> ---
> net/ipv4/ip_tunnel.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
> index 64594aa..ad78825 100644
> --- a/net/ipv4/ip_tunnel.c
> +++ b/net/ipv4/ip_tunnel.c
> @@ -317,7 +317,7 @@ static int ip_tunnel_bind_dev(struct net_device *dev)
> }
>
> dev->needed_headroom = t_hlen + hlen;
> - mtu -= (dev->hard_header_len + t_hlen);
> + mtu -= dev->hard_header_len ? : t_hlen;
Safety of this change also depends on whether any other ip tunnels
might have non-zero hard_header_len.
I haven't fully checked yet, but at first scan I only see one other
instance of header_ops, and that ip_tunnel_header_ops does not have a
create implementation.
>
> if (mtu < IPV4_MIN_MTU)
> mtu = IPV4_MIN_MTU;
> @@ -347,7 +347,7 @@ static struct ip_tunnel *ip_tunnel_create(struct net *net,
> nt = netdev_priv(dev);
> t_hlen = nt->hlen + sizeof(struct iphdr);
> dev->min_mtu = ETH_MIN_MTU;
> - dev->max_mtu = IP_MAX_MTU - dev->hard_header_len - t_hlen;
> + dev->max_mtu = IP_MAX_MTU - dev->hard_header_len ? : t_hlen;
here and elsewhere: subtraction takes precedence over ternary
conditional, so (IP_MAX_MTU - ..) always true.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [net] net: ip_tunnel: fix mtu calculation
2021-01-28 21:48 ` Willem de Bruijn
@ 2021-01-29 0:56 ` Vadim Fedorenko
0 siblings, 0 replies; 3+ messages in thread
From: Vadim Fedorenko @ 2021-01-29 0:56 UTC (permalink / raw)
To: Willem de Bruijn
Cc: Jakub Kicinski, Cong Wang, Slava Bacherikov, Network Development
On 28.01.2021 21:48, Willem de Bruijn wrote:
> On Wed, Jan 27, 2021 at 11:14 PM Vadim Fedorenko <vfedorenko@novek.ru> wrote:
>>
>> dev->hard_header_len for tunnel interface is set only when header_ops
>> are set too and already contains full overhead of any tunnel encapsulation.
>> That's why there is not need to use this overhead twice in mtu calc.
>>
>> Fixes: fdafed459998 ("ip_gre: set dev->hard_header_len and dev->needed_headroom properly")
>> Reported-by: Slava Bacherikov <mail@slava.cc>
>> Signed-off-by: Vadim Fedorenko <vfedorenko@novek.ru>
>> ---
>> net/ipv4/ip_tunnel.c | 18 +++++++++---------
>> 1 file changed, 9 insertions(+), 9 deletions(-)
>>
>> diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
>> index 64594aa..ad78825 100644
>> --- a/net/ipv4/ip_tunnel.c
>> +++ b/net/ipv4/ip_tunnel.c
>> @@ -317,7 +317,7 @@ static int ip_tunnel_bind_dev(struct net_device *dev)
>> }
>>
>> dev->needed_headroom = t_hlen + hlen;
>> - mtu -= (dev->hard_header_len + t_hlen);
>> + mtu -= dev->hard_header_len ? : t_hlen;
>
> Safety of this change also depends on whether any other ip tunnels
> might have non-zero hard_header_len.
Yes, sure.
> I haven't fully checked yet, but at first scan I only see one other
> instance of header_ops, and that ip_tunnel_header_ops does not have a
> create implementation.
Yes. The calls to ip_tunnel_setup are in ip_gre.c, ip_tunnel.c, ip_vti.c
and ipip.c. All of them except of ip_gre use ip_tunnel_header_ops which
doesn't have create implementation and have hard_header_len set to 0.
>
>>
>> if (mtu < IPV4_MIN_MTU)
>> mtu = IPV4_MIN_MTU;
>> @@ -347,7 +347,7 @@ static struct ip_tunnel *ip_tunnel_create(struct net *net,
>> nt = netdev_priv(dev);
>> t_hlen = nt->hlen + sizeof(struct iphdr);
>> dev->min_mtu = ETH_MIN_MTU;
>> - dev->max_mtu = IP_MAX_MTU - dev->hard_header_len - t_hlen;
>> + dev->max_mtu = IP_MAX_MTU - dev->hard_header_len ? : t_hlen;
>
> here and elsewhere: subtraction takes precedence over ternary
> conditional, so (IP_MAX_MTU - ..) always true.
Oh, sure, my bad. Will fix it in v2, thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-01-28 3:48 [net] net: ip_tunnel: fix mtu calculation Vadim Fedorenko
2021-01-28 21:48 ` Willem de Bruijn
2021-01-29 0:56 ` Vadim Fedorenko
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