Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
And some nitpicks below...
On Tue, 28 Aug 2012, Patrick McHardy wrote:
The IPv6 conntrack fragmentation currently has a couple of shortcomings.
Fragmentes are collected in PREROUTING/OUTPUT, are defragmented, the
defragmented packet is then passed to conntrack, the resulting conntrack
information is attached to each original fragment and the fragments then
continue their way through the stack.
Helper invocation occurs in the POSTROUTING hook, at which point only
the original fragments are available. The result of this is that
fragmented packets are never passed to helpers.
This patch improves the situation in the following way:
- If a reassembled packet belongs to a connection that has a helper
assigned, the reassembled packet is passed through the stack instead
of the original fragments.
- During defragmentation, the largest received fragment size is stored.
On output, the packet is refragmented if required. If the largest
received fragment size exceeds the outgoing MTU, a "packet too big"
message is generated, thus behaving as if the original fragments
were passed through the stack from an outside point of view.
- The ipv6_helper() hook function can't receive fragments anymore for
connections using a helper, so it is switched to use ipv6_skip_exthdr()
instead of the netfilter specific nf_ct_ipv6_skip_exthdr() and the
reassembled packets are passed to connection tracking helpers.
The result of this is that we can properly track fragmented packets, but
still generate ICMPv6 Packet too big messages if we would have before.
This patch is also required as a precondition for IPv6 NAT, where NAT
helpers might enlarge packets up to a point that they require
fragmentation. In that case we can't generate Packet too big messages
since the proper MTU can't be calculated in all cases (f.i. when
changing textual representation of a variable amount of addresses),
so the packet is transparently fragmented iff the original packet or
fragments would have fit the outgoing MTU.
IPVS parts by Jesper Dangaard Brouer <brouer@xxxxxxxxxx>.
Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx>
---
include/linux/ipv6.h | 1 +
net/ipv6/ip6_output.c | 7 +++-
net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c | 41 ++++++++++++++++++-----
net/ipv6/netfilter/nf_conntrack_reasm.c | 19 +++++++++--
net/netfilter/ipvs/ip_vs_xmit.c | 9 +++++-
5 files changed, 62 insertions(+), 15 deletions(-)
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 879db26..0b94e91 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -256,6 +256,7 @@ struct inet6_skb_parm {
#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
__u16 dsthao;
#endif
+ __u16 frag_max_size;
#define IP6SKB_XFRM_TRANSFORMED 1
#define IP6SKB_FORWARDED 2
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 5b2d63e..a4f6263 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -493,7 +493,8 @@ int ip6_forward(struct sk_buff *skb)
if (mtu < IPV6_MIN_MTU)
mtu = IPV6_MIN_MTU;
- if (skb->len > mtu && !skb_is_gso(skb)) {
+ if ((!skb->local_df && skb->len > mtu && !skb_is_gso(skb)) ||
You use (!skb->local_df) to invalidate the use of skb->len, instead of
(!IP6CB(skb)->frag_max_size), (which is okay, because you set local_df
later). Is there are reason this check is better?
+ (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu)) {
Eric Dumazet would probably nitpick and say, it can be reduced to:
(IP6CB(skb)->frag_max_size > mtu)
;-)
/* Again, force OUTPUT device used as source address */
skb->dev = dst->dev;
icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
@@ -636,7 +637,9 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
/* We must not fragment if the socket is set to force MTU discovery
* or if the skb it not generated by a local socket.
*/
- if (unlikely(!skb->local_df && skb->len > mtu)) {
+ if (unlikely(!skb->local_df && skb->len > mtu) ||
+ (IP6CB(skb)->frag_max_size &&
+ IP6CB(skb)->frag_max_size > mtu)) {
if (skb->sk && dst_allfrag(skb_dst(skb)))
sk_nocaps_add(skb->sk, NETIF_F_GSO_MASK);
[cut]
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -190,6 +190,7 @@ static int nf_ct_frag6_queue(struct nf_ct_frag6_queue *fq, struct sk_buff *skb,
const struct frag_hdr *fhdr, int nhoff)
{
struct sk_buff *prev, *next;
+ unsigned int payload_len;
int offset, end;
if (fq->q.last_in & INET_FRAG_COMPLETE) {
@@ -197,8 +198,10 @@ static int nf_ct_frag6_queue(struct nf_ct_frag6_queue *fq, struct sk_buff *skb,
goto err;
}
+ payload_len = ntohs(ipv6_hdr(skb)->payload_len);
+
offset = ntohs(fhdr->frag_off) & ~0x7;
- end = offset + (ntohs(ipv6_hdr(skb)->payload_len) -
+ end = offset + (payload_len -
((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
if ((unsigned int)end > IPV6_MAXPLEN) {
@@ -307,6 +310,8 @@ found:
skb->dev = NULL;
fq->q.stamp = skb->tstamp;
fq->q.meat += skb->len;
+ if (payload_len > fq->q.max_size)
+ fq->q.max_size = payload_len;
atomic_add(skb->truesize, &nf_init_frags.mem);
/* The first fragment.
@@ -412,10 +417,12 @@ nf_ct_frag6_reasm(struct nf_ct_frag6_queue *fq, struct net_device *dev)
}
atomic_sub(head->truesize, &nf_init_frags.mem);
+ head->local_df = 1;
/me pointing to where local_df is being set.
head->next = NULL;
head->dev = dev;
head->tstamp = fq->q.stamp;
ipv6_hdr(head)->payload_len = htons(payload_len);
+ IP6CB(head)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
/* Yes, and fold redundant checksum back. 8) */
if (head->ip_summed == CHECKSUM_COMPLETE)
[cut]
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