RE: Fix for Real Audio IP Masquerade

[Villalovos, John L]

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Also attaching a file of the diff since stuff got munged through the email.

-----Original Message-----
From: Villalovos, John L [mailto:[e-mail]]
Sent: Wednesday, January 03, 2001 4:17 PM
To: '[e-mail]'
Cc: '[e-mail]'
Subject: Fix for Real Audio IP Masquerade

Diff against 2.2.19pre6 though the file hasn't changed since Oct 27, 1998.

This fixes a problem in the ip_masq_raudio.c module where it assumes that
all TCP headers are 20 bytes long.  Some implementations of the Real Player
clients use the TCP options section of the TCP header.  Thus these TCP
headers are longer than 20 bytes long and then break the RTSP portion of the
IP masquerading code.  This fix uses the header length field in the TCP
header to calculate the correct offset into the data portion of the TCP
packet.

John

--- ip_masq_raudio.c	Tue Oct 27 09:57:19 1998
+++ /usr/src/linux/net/ipv4/ip_masq_raudio.c	Wed Jan  3 16:03:21 2001
@@ -169,7 +169,10 @@
         skb = *skb_p;
 	iph = skb->nh.iph;
         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
-        data = (char *)&th[1];
+
+	/* Make sure we take into account the size of the TCP packet.  This
is
+	 * because there may be TCP options in the TCP packet */
+	data = ((char *)&th[0]) + (th->doff * 4);
 
         data_limit = skb->h.raw + skb->len;
 
@@ -315,7 +318,10 @@
         skb = *skb_p;
 	iph = skb->nh.iph;
         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
-        data = (char *)&th[1];
+
+	/* Make sure we take into account the size of the TCP packet.  This
is
+	 * because there may be TCP options in the TCP packet */
+	data = ((char *)&th[0]) + (th->doff * 4);
 
         data_limit = skb->h.raw + skb->len;
 
John Villalovos
Intel Corporation
2111 NE 25TH AVE STOP JF2-70
HILLSBORO, OR  97124-5961
[phone]   Fax: [phone]

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--- ip_masq_raudio.c	Tue Oct 27 09:57:19 1998=0A=
+++ /usr/src/linux/net/ipv4/ip_masq_raudio.c	Wed Jan  3 16:03:21 =
2001=0A=
@@ -169,7 +169,10 @@=0A=
         skb =3D *skb_p;=0A=
 	iph =3D skb->nh.iph;=0A=
         th =3D (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);=0A=
-        data =3D (char *)&th[1];=0A=
+=0A=
+	/* Make sure we take into account the size of the TCP packet.  This =
is=0A=
+	 * because there may be TCP options in the TCP packet */=0A=
+	data =3D ((char *)&th[0]) + (th->doff * 4);=0A=
 =0A=
         data_limit =3D skb->h.raw + skb->len;=0A=
 =0A=
@@ -315,7 +318,10 @@=0A=
         skb =3D *skb_p;=0A=
 	iph =3D skb->nh.iph;=0A=
         th =3D (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);=0A=
-        data =3D (char *)&th[1];=0A=
+=0A=
+	/* Make sure we take into account the size of the TCP packet.  This =
is=0A=
+	 * because there may be TCP options in the TCP packet */=0A=
+	data =3D ((char *)&th[0]) + (th->doff * 4);=0A=
 =0A=
         data_limit =3D skb->h.raw + skb->len;=0A=
 =0A=

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