* [PATCH] netfilter: ipv4: defrag: set local_df flag on defragmented skb
@ 2014-05-02 13:32 Florian Westphal
2014-05-04 4:45 ` Maciej Żenczykowski
2014-05-04 11:24 ` Pablo Neira Ayuso
0 siblings, 2 replies; 4+ messages in thread
From: Florian Westphal @ 2014-05-02 13:32 UTC (permalink / raw)
To: netfilter-devel; +Cc: Florian Westphal
else we may fail to forward skb even if original fragments do fit
outgoing link mtu:
1. remote sends 2k packets in two 1000 byte frags, DF set
2. we want to forward but only see '2k > mtu and DF set'
3. we then send icmp error saying that outgoing link is 1500
But original sender never sent a packet that would not fit
the outgoing link.
Setting local_df makes outgoing path test size vs.
IPCB(skb)->frag_max_size, so we will still send the correct
error in case the largest original size did not fit
outgoing link mtu.
Reported-by: Maxime Bizon <mbizon@freebox.fr>
Suggested-by: Maxime Bizon <mbizon@freebox.fr>
Fixes: 5f2d04f1f9 (ipv4: fix path MTU discovery with connection tracking)
Signed-off-by: Florian Westphal <fw@strlen.de>
---
diff --git a/net/ipv4/netfilter/nf_defrag_ipv4.c b/net/ipv4/netfilter/nf_defrag_ipv4.c
index 12e13bd..f40f321 100644
--- a/net/ipv4/netfilter/nf_defrag_ipv4.c
+++ b/net/ipv4/netfilter/nf_defrag_ipv4.c
@@ -22,7 +22,6 @@
#endif
#include <net/netfilter/nf_conntrack_zones.h>
-/* Returns new sk_buff, or NULL */
static int nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
{
int err;
@@ -33,8 +32,10 @@ static int nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
err = ip_defrag(skb, user);
local_bh_enable();
- if (!err)
+ if (!err) {
ip_send_check(ip_hdr(skb));
+ skb->local_df = 1;
+ }
return err;
}
--
1.8.1.5
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] netfilter: ipv4: defrag: set local_df flag on defragmented skb
2014-05-02 13:32 [PATCH] netfilter: ipv4: defrag: set local_df flag on defragmented skb Florian Westphal
@ 2014-05-04 4:45 ` Maciej Żenczykowski
2014-05-04 10:16 ` Florian Westphal
2014-05-04 11:24 ` Pablo Neira Ayuso
1 sibling, 1 reply; 4+ messages in thread
From: Maciej Żenczykowski @ 2014-05-04 4:45 UTC (permalink / raw)
To: Florian Westphal; +Cc: Netfilter Development Mailinglist
Are you deleting the comment because it is incorrect?
On Fri, May 2, 2014 at 6:32 AM, Florian Westphal <fw@strlen.de> wrote:
> else we may fail to forward skb even if original fragments do fit
> outgoing link mtu:
>
> 1. remote sends 2k packets in two 1000 byte frags, DF set
> 2. we want to forward but only see '2k > mtu and DF set'
> 3. we then send icmp error saying that outgoing link is 1500
>
> But original sender never sent a packet that would not fit
> the outgoing link.
>
> Setting local_df makes outgoing path test size vs.
> IPCB(skb)->frag_max_size, so we will still send the correct
> error in case the largest original size did not fit
> outgoing link mtu.
>
> Reported-by: Maxime Bizon <mbizon@freebox.fr>
> Suggested-by: Maxime Bizon <mbizon@freebox.fr>
> Fixes: 5f2d04f1f9 (ipv4: fix path MTU discovery with connection tracking)
> Signed-off-by: Florian Westphal <fw@strlen.de>
> ---
> diff --git a/net/ipv4/netfilter/nf_defrag_ipv4.c b/net/ipv4/netfilter/nf_defrag_ipv4.c
> index 12e13bd..f40f321 100644
> --- a/net/ipv4/netfilter/nf_defrag_ipv4.c
> +++ b/net/ipv4/netfilter/nf_defrag_ipv4.c
> @@ -22,7 +22,6 @@
> #endif
> #include <net/netfilter/nf_conntrack_zones.h>
>
> -/* Returns new sk_buff, or NULL */
> static int nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
> {
> int err;
> @@ -33,8 +32,10 @@ static int nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
> err = ip_defrag(skb, user);
> local_bh_enable();
>
> - if (!err)
> + if (!err) {
> ip_send_check(ip_hdr(skb));
> + skb->local_df = 1;
> + }
>
> return err;
> }
> --
> 1.8.1.5
>
> --
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] netfilter: ipv4: defrag: set local_df flag on defragmented skb
2014-05-02 13:32 [PATCH] netfilter: ipv4: defrag: set local_df flag on defragmented skb Florian Westphal
2014-05-04 4:45 ` Maciej Żenczykowski
@ 2014-05-04 11:24 ` Pablo Neira Ayuso
1 sibling, 0 replies; 4+ messages in thread
From: Pablo Neira Ayuso @ 2014-05-04 11:24 UTC (permalink / raw)
To: Florian Westphal; +Cc: netfilter-devel
On Fri, May 02, 2014 at 03:32:16PM +0200, Florian Westphal wrote:
> else we may fail to forward skb even if original fragments do fit
> outgoing link mtu:
>
> 1. remote sends 2k packets in two 1000 byte frags, DF set
> 2. we want to forward but only see '2k > mtu and DF set'
> 3. we then send icmp error saying that outgoing link is 1500
>
> But original sender never sent a packet that would not fit
> the outgoing link.
>
> Setting local_df makes outgoing path test size vs.
> IPCB(skb)->frag_max_size, so we will still send the correct
> error in case the largest original size did not fit
> outgoing link mtu.
Thanks Florian for picking up this issue posted in netdev and cooking
a patch for it. Enqueued to the nf tree.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2014-05-02 13:32 [PATCH] netfilter: ipv4: defrag: set local_df flag on defragmented skb Florian Westphal
2014-05-04 4:45 ` Maciej Żenczykowski
2014-05-04 10:16 ` Florian Westphal
2014-05-04 11:24 ` Pablo Neira Ayuso
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