On 03/08/2018 07:01 AM, Serhey Popovych wrote:
Eric Dumazet wrote:
On 03/08/2018 02:08 AM, Serhey Popovych wrote:
We can't use skb_reset_transport_header() together with skb_put() to set
skb->transport_header field because skb_put() does not touch skb->data.
Do this same way as we did for csum_data in code: substract skb->head
from tcph.
Signed-off-by: Serhey Popovych <serhe.popovych@xxxxxxxxx>
---
net/ipv4/netfilter/ipt_SYNPROXY.c | 8 ++++----
net/ipv6/netfilter/ip6t_SYNPROXY.c | 8 ++++----
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c
b/net/ipv4/netfilter/ipt_SYNPROXY.c
index f75fc6b..4953390 100644
--- a/net/ipv4/netfilter/ipt_SYNPROXY.c
+++ b/net/ipv4/netfilter/ipt_SYNPROXY.c
@@ -90,8 +90,8 @@
niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
- skb_reset_transport_header(nskb);
nth = skb_put(nskb, tcp_hdr_size);
+ nskb->transport_header = (unsigned char *)nth - nskb->head;
I have no idea why you believe the current code is not correct.
alloc_skb():
skb->head = skb->data = skb_tail_pointer(skb)
synproxy_build_ip():
skb_reset_network_header() /* skb_network_header(skb) == skb->data */
skb_put(skb, len); /* skb->tail += len; skb->len += len */
nth = skb_put() : nth is equal to skb->data
Yes it is equal to skb->data, but in my opinion should be set to
skb->data + ip_hdrlen(skb) to point to TCP header.
Is it really needed to set transport header offset ? We do not intend to
inject this packet to a local TCP stack ?
Nothing will care of transport header for non GSO packet.
Anyway, maybe the confusion would be avoided if the normal way of
pushing headers would be used (using skb_push())
No casts requested ;)
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