Entirely ignoring TCP and UDP checksum in kernel level
Quoted 9 lines · Josan Kadett
Here is the very original linux-kernel mailing list, and if I cannot find an answer here, then nowhere on earth can this answer be found. I also saw some other messages regarding the same issue on the net. None of them is answered correctly; and also as if this is a very "forbidden" thing to disable the checksums, most replies are as if they are "unbreakable rules of god". Really, I am losing my patience with this. It is also very odd to write a low-level application in order to just disable a "feature" of the kernel to deal with a faulty piece of embedded firmware.
Try this. I have no idea whether it will work. If it breaks you get to keep both halves.
ipv4/tcp_input.c-new renamed from ipv4/tcp_input.c +2 -3
@@ -4234,8 +4234,7 @@ } } if (!eaten) { - if (tcp_checksum_complete_user(sk, skb)) - goto csum_error; + tcp_checksum_complete_user(sk, skb); /* Predicted packet is in window by definition. * seq == rcv_nxt and rcv_wup <= rcv_nxt.
@@ -4291,7 +4290,7 @@ slow_path: if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb)) - goto csum_error; + ; /* * RFC1323: H1. Apply PAWS check first.
Lee
I added the patch, indeed this was just one of the few modifications I tried before. The result is failure, the TCP/IP stack still does the checksum... Perhaps after this modification, the condition that the packet is not "eaten" may not be telling the system that there is a checksum error, but instead, just dropping packets by not igniting the TCP ACK function.
-----Original Message-----
From: Lee Revell [mailto:[email protected]]
Sent: Saturday, August 21, 2004 10:58 AM
To: Josan Kadett
Cc: linux-kernel
Subject: RE: Entirely ignoring TCP and UDP checksum in kernel level
Quoted 1 line · Josan Kadett
Here is the very original linux-kernel mailing list, and if I cannot find
an
Quoted 1 line
answer here, then nowhere on earth can this answer be found. I also saw
some
Quoted 1 line
other messages regarding the same issue on the net. None of them is
answered
Quoted 4 lines
correctly; and also as if this is a very "forbidden" thing to disable the checksums, most replies are as if they are "unbreakable rules of god". Really, I am losing my patience with this. It is also very odd to write a low-level application in order to just disable a "feature" of the kernel
to
Quoted 2 lines
deal with a faulty piece of embedded firmware.
Try this. I have no idea whether it will work. If it breaks you get to keep both halves.
ipv4/tcp_input.c-new renamed from ipv4/tcp_input.c +1 -2
@@ -4234,8 +4234,7 @@ } } if (!eaten) { - if (tcp_checksum_complete_user(sk, skb)) - goto csum_error; + tcp_checksum_complete_user(sk, skb); /* Predicted packet is in window by
definition.
* seq == rcv_nxt and rcv_wup <= rcv_nxt.
@@ -4291,7 +4290,7 @@
slow_path:
if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
- goto csum_error;
+ ;
/*
* RFC1323: H1. Apply PAWS check first.
Lee