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SubjectRe: question on ip_masq_irc.c
On Thu, 29 Mar 2001, Deja User wrote:
> I am working on a NAT product and trying provide mIRC support in it. I am looking into ip_masq_irc.c file of Linux 2.2.12 for reference, and have some doubts.
> 1. In 2.2.12 ip_masq_irc.c, DCC RESUME protocol is not supported. In which patch can I find it?
> 2. I have pre-patch-2.2.18-5 linux.18p5/net/ipv4/ip_masq_irc.c, which has support for DCC RESUME. Is this the final patch? I have checked with documentation in mIRC help files about DCC RESUME command string. It says the command string in the pay load looks
> DCC RESUME filename port position
> But, in the above file, the string hunted is
> "\1DCC RESUME chat AAAAAAAA P\1\n"

You're right, it's broken. I submitted a patch for people to test, but
somehow it got into the production kernel without testing.

I created a second patch shortly after realizing the problem, tested and
submitted it, but it doesn't look like it ever made it in.

I'm including the patch. It's a diff against the ip_masq_irc.c from 2.2.17
(which was current at the time), so you may have to get this file
seperately if you're not using 2.2.17. Many apologies.

Scottie Shore | "Experience is the worst teacher -
<sshore@escape.ca> | it teaches you what you need to know
| after you needed to know it."

--- ip_masq_irc.c.orig Wed Sep 27 22:07:15 2000
+++ ip_masq_irc.c Sun Oct 1 21:30:41 2000
@@ -20,9 +20,11 @@
* Juan Jose Ciarlante : put new ms entry to listen()
* Scottie Shore : added support for clients that add extra args
* <sshore@escape.ca>
+ * Scottie Shore : added support for mIRC DCC resume negotiation
+ * <sshore@escape.ca>
*
- * FIXME:
- * - detect also previous "PRIVMSG" string ?.
+ * FIXME: take common code from ip_masq_in and ip_masq_out, put into seperate
+ * function
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@@ -78,22 +80,24 @@
* List of supported DCC protocols
*/

-#define NUM_DCCPROTO 5
+#define NUM_DCCPROTO 6

struct dccproto
{
char *match;
int matchlen;
+ int addr;
};

struct dccproto dccprotos[NUM_DCCPROTO] = {
- { "SEND ", 5 },
- { "CHAT ", 5 },
- { "MOVE ", 5 },
- { "TSEND ", 6 },
- { "SCHAT ", 6 }
+ { "SEND ", 5, 1 },
+ { "CHAT ", 5, 1 },
+ { "MOVE ", 5, 1 },
+ { "TSEND ", 6, 1 },
+ { "SCHAT ", 6, 1 },
+ { "ACCEPT ", 7, 0 },
};
-#define MAXMATCHLEN 6
+#define MAXMATCHLEN 7

static int
masq_irc_init_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
@@ -118,7 +122,7 @@
char *data, *data_limit;
__u32 s_addr;
__u16 s_port;
- struct ip_masq *n_ms;
+ struct ip_masq *n_ms = NULL;
char buf[20]; /* "m_addr m_port" (dec base)*/
unsigned buf_len;
int diff;
@@ -137,16 +141,18 @@
* strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26
* strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26
* strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27
+ * strlen("\1DCC ACCEPT F P O\1\n")=19
* AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits)
* P: bound port (min 1 d )
* F: filename (min 1 d )
* S: size (min 1 d )
+ * O: offset (min 1 d )
* 0x01, \n: terminators
*/

data_limit = skb->h.raw + skb->len;

- while (data < (data_limit - ( 22 + MAXMATCHLEN ) ) )
+ while (data < (data_limit - ( 12 + MAXMATCHLEN ) ) )
{
int i;
if (memcmp(data,"\1DCC ",5)) {
@@ -171,52 +177,60 @@
* skip next string.
*/

- while( *data++ != ' ')
+ while ( *data++ != ' ')
+ if (data > (data_limit-5)) return 0;
+ addr_beg_p = data;

+ if (dccprotos[i].addr == 1)
+ {
/*
- * must still parse, at least, "AAAAAAAA P\1\n",
- * 12 bytes left.
+ * client bound address in dec base
*/
- if (data > (data_limit-12)) return 0;
-
-
- addr_beg_p = data;

- /*
- * client bound address in dec base
- */
-
- s_addr = simple_strtoul(data,&data,10);
- if (*data++ !=' ')
- continue;
+ s_addr = simple_strtoul(data,&data,10);
+ if (*data++ !=' ')
+ continue;

- /*
- * client bound port in dec base
- */
+ /*
+ * client bound port in dec base
+ */

- s_port = simple_strtoul(data,&data,10);
- addr_end_p = data;
+ s_port = simple_strtoul(data,&data,10);
+ addr_end_p = data;

- /*
- * Now create an masquerade entry for it
- * must set NO_DPORT and NO_DADDR because
- * connection is requested by another client.
- */
+ /*
+ * We must set NO_DPORT and NO_DADDR because
+ * connection is requested by another client.
+ */

- n_ms = ip_masq_new(IPPROTO_TCP,
+ n_ms = ip_masq_new(IPPROTO_TCP,
maddr, 0,
htonl(s_addr),htons(s_port),
0, 0,
IP_MASQ_F_NO_DPORT|IP_MASQ_F_NO_DADDR);
- if (n_ms==NULL)
- return 0;

- /*
- * Replace the old "address port" with the new one
- */
+ if (n_ms==NULL)
+ return 0;
+ ip_masq_listen(n_ms);

- buf_len = sprintf(buf,"%lu %u",
+ /*
+ * Replace the old "address port" with the new one
+ */
+ buf_len = sprintf(buf,"%lu %u",
ntohl(n_ms->maddr),ntohs(n_ms->mport));
+ } else {
+ /* client bound port in decimal */
+ s_port = simple_strtoul(data,&data,10);
+ addr_end_p = data;
+
+ n_ms = ip_masq_out_get (IPPROTO_TCP,
+ ms->saddr,htons(s_port),
+ 0, 0);
+ if (n_ms == NULL)
+ return 0;
+
+ buf_len = sprintf(buf,"%u",ntohs(n_ms->mport));
+ }

/*
* Calculate required delta-offset to keep TCP happy
@@ -242,7 +256,6 @@
addr_beg_p, addr_end_p-addr_beg_p,
buf, buf_len);
}
- ip_masq_listen(n_ms);
ip_masq_put(n_ms);
return diff;
}
@@ -252,6 +265,122 @@

}

+int
+masq_irc_in (struct ip_masq_app *mapp, struct ip_masq *ms, struct sk_buff **skb_p, __u32 maddr)
+{
+ struct sk_buff *skb;
+ struct iphdr *iph;
+ struct tcphdr *th;
+ char *data, *data_limit;
+ __u32 s_addr;
+ __u16 s_port;
+ struct ip_masq *n_ms;
+ char buf[20]; /* "m_addr m_port" (dec base)*/
+ unsigned buf_len;
+ int diff;
+ char *dcc_p, *addr_beg_p, *addr_end_p;
+
+ skb = *skb_p;
+ iph = skb->nh.iph;
+ th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
+ data = (char *)&th[1];
+
+ /*
+ * Hunt irc DCC RESUME string:
+ *
+ * strlen("\1DCC RESUME F P O\1\n")=19
+ * F: filename (min 1 c )
+ * P: bound port (min 1 d )
+ * O: offset (min 1 d )
+ * 0x01, \n: terminators
+ */
+
+ data_limit = skb->h.raw + skb->len;
+
+ while (data < (data_limit - 19 ) )
+ {
+ if (memcmp(data,"\1DCC RESUME ",12)) {
+ data ++;
+ continue;
+ }
+
+ dcc_p = data;
+ data += 12;
+
+ while( *data++ != ' ')
+ /*
+ * must still parse, at least, "F P O\1\n",
+ * 7 bytes left.
+ */
+ if (data > (data_limit-7)) return 0;
+
+
+ addr_beg_p = data;
+
+ /*
+ * masq bound port in dec base
+ */
+
+ s_port = simple_strtoul(data,&data,10);
+ addr_end_p = data;
+
+ /*
+ * Find the masq entry associated with this connection.
+ * The entry should have no dest addr/port yet.
+ * If there is no entry, return 0.
+ *
+ * mIRC & co. assume that a port can uniquely identify
+ * a connection. It's true 99% of the time, but it's still
+ * a stupid assumption.
+ */
+
+ n_ms = ip_masq_in_get(IPPROTO_TCP,
+ 0, 0,
+ ms->maddr, htons(s_port));
+
+ if (n_ms==NULL) {
+ return 0;
+ } else {
+ ip_masq_put(n_ms);
+ }
+
+ /*
+ * Replace the outside address with the inside address
+ */
+
+ buf_len = sprintf(buf,"%u",
+ ntohs(n_ms->sport));
+
+ /*
+ * Calculate required delta-offset to keep TCP happy
+ */
+
+ diff = buf_len - (addr_end_p-addr_beg_p);
+
+ *addr_beg_p = '\0';
+
+ /*
+ * No shift.
+ */
+
+ if (diff==0) {
+ /*
+ * simple case, just copy.
+ */
+ memcpy(addr_beg_p,buf,buf_len);
+ } else {
+ *skb_p = ip_masq_skb_replace(skb, GFP_ATOMIC,
+ addr_beg_p, addr_end_p-addr_beg_p,
+ buf, buf_len);
+ }
+
+ return diff;
+
+ }
+ return 0;
+
+}
+
/*
* Main irc object
* You need 1 object per port in case you need
@@ -263,12 +392,12 @@
struct ip_masq_app ip_masq_irc = {
NULL, /* next */
"irc", /* name */
- 0, /* type */
- 0, /* n_attach */
- masq_irc_init_1, /* init_1 */
- masq_irc_done_1, /* done_1 */
- masq_irc_out, /* pkt_out */
- NULL /* pkt_in */
+ 0, /* type */
+ 0, /* n_attach */
+ masq_irc_init_1, /* init_1 */
+ masq_irc_done_1, /* done_1 */
+ masq_irc_out, /* pkt_out */
+ masq_irc_in /* pkt_in */
};

/*

-
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