#include <linux/gfp.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/textsearch.h>
#include <linux/version.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <net/tcp.h>
#include <net/udp.h>
#if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 12, 0)
#	include <linux/unaligned.h>
#else
#	include <asm/unaligned.h>
#endif
#include "xt_ipp2p.h"
#include "compat_xtables.h"
#if !defined(CONFIG_TEXTSEARCH_BM) && !defined(CONFIG_TEXTSEARCH_BM_MODULE)
#	error CONFIG_TEXTSEARCH_BM=y/m is required for ipp2p. Either enable textsearch in your kernel ".config" file, or disable ipp2p in the "mconfig" file in Xtables-addons.
#endif

//#define IPP2P_DEBUG_ARES
//#define IPP2P_DEBUG_SOUL
//#define IPP2P_DEBUG_WINMX

#define get_u8(X,  O)  (*(const __u8 *)((X) + O))
#define get_u16(X, O)  get_unaligned((const __u16 *)((X) + O))
#define get_u32(X, O)  get_unaligned((const __u32 *)((X) + O))

#define TEXTSEARCH_ALGO "kmp"

MODULE_AUTHOR("Eicke Friedrich/Klaus Degner <ipp2p@ipp2p.org>");
MODULE_DESCRIPTION("An extension to iptables to identify P2P traffic.");
MODULE_LICENSE("GPL");

#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 1, 0)
static inline unsigned int
ip_transport_len(const struct sk_buff *skb)
{
        return ntohs(ip_hdr(skb)->tot_len) - skb_network_header_len(skb);
}
static inline unsigned int
ipv6_transport_len(const struct sk_buff *skb)
{
        return ntohs(ipv6_hdr(skb)->payload_len) + sizeof(struct ipv6hdr) -
               skb_network_header_len(skb);
}
#endif

struct ipp2p_result_printer {
	const union nf_inet_addr *saddr, *daddr;
	short sport, dport;
	void (*print)(const union nf_inet_addr *, short,
		      const union nf_inet_addr *, short,
		      bool, unsigned int);
};

static bool iscrlf(const unsigned char *str)
{
	return str[0] == '\r' && str[1] == '\n';
}

static void
print_result(const struct ipp2p_result_printer *rp, bool result,
             unsigned int hlen)
{
	rp->print(rp->saddr, rp->sport,
		  rp->daddr, rp->dport,
		  result, hlen);
}

/* Search for UDP eDonkey/eMule/Kad commands */
static unsigned int
udp_search_edk(const struct sk_buff *skb,
	       const unsigned int packet_off,
	       const unsigned int packet_len,
	       const struct ipt_p2p_info *info)
{
	unsigned char buf[36], *t;

	if (packet_len < 4)
		return 0;

	t = skb_header_pointer(skb, packet_off,
			       packet_len < sizeof(buf) ?
			       packet_len : sizeof(buf),
			       buf);
	if (t == NULL)
		return 0;

	switch (t[0]) {
	case 0xe3:
		/* eDonkey */
		switch (t[1]) {
		/* client -> server status request */
		case 0x96:
			if (packet_len == 6)
				return IPP2P_EDK * 100 + 50;
			break;

		/* server -> client status request */
		case 0x97:
			if (packet_len == 34)
				return IPP2P_EDK * 100 + 51;
			break;

		/* server description request */
		/* e3 2a ff f0 .. | size == 6 */
		case 0xa2:
			if (packet_len == 6 &&
			    get_u16(t, 2) == __constant_htons(0xfff0))
				return IPP2P_EDK * 100 + 52;
			break;

		/* server description response */
		/* e3 a3 ff f0 ..  | size > 40 && size < 200 */
		/*
		case 0xa3:
			return IPP2P_EDK * 100 + 53;
			break;
		*/

		case 0x9a:
			if (packet_len == 18)
				return IPP2P_EDK * 100 + 54;
			break;

		case 0x92:
			if (packet_len == 10)
				return IPP2P_EDK * 100 + 55;
			break;
		}
		break;

	case 0xe4:
		switch (t[1]) {
		/* e4 20 .. | size == 35 */
		case 0x20:
			if (packet_len == 35 && t[2] != 0x00 && t[34] != 0x00)
				return IPP2P_EDK * 100 + 60;
			break;

		/* e4 00 .. 00 | size == 27 ? */
		case 0x00:
			if (packet_len == 27 && t[26] == 0x00)
				return IPP2P_EDK * 100 + 61;
			break;

		/* e4 10 .. 00 | size == 27 ? */
		case 0x10:
			if (packet_len == 27 && t[26] == 0x00)
				return IPP2P_EDK * 100 + 62;
			break;

		/* e4 18 .. 00 | size == 27 ? */
		case 0x18:
			if (packet_len == 27 && t[26] == 0x00)
				return IPP2P_EDK * 100 + 63;
			break;

		/* e4 52 .. | size = 36 */
		case 0x52:
			if (packet_len == 36)
				return IPP2P_EDK * 100 + 64;
			break;

		/* e4 58 .. | size == 6 */
		case 0x58:
			if (packet_len == 6)
				return IPP2P_EDK * 100 + 65;
			break;

		/* e4 59 .. | size == 2 */
		case 0x59:
			if (packet_len == 2)
				return IPP2P_EDK * 100 + 66;
			break;

		/* e4 28 .. | packet_len == 49,69,94,119... */
		case 0x28:
			if ((packet_len - 44) % 25 == 0)
				return IPP2P_EDK * 100 + 67;
			break;

		/* e4 50 xx xx | size == 4 */
		case 0x50:
			if (packet_len == 4)
				return IPP2P_EDK * 100 + 68;
			break;

		/* e4 40 xx xx | size == 48 */
		case 0x40:
			if (packet_len == 48)
				return IPP2P_EDK * 100 + 69;
			break;
		}
		break;
	}
	return 0;
}

/* Search for UDP Gnutella commands */
static unsigned int
udp_search_gnu(const struct sk_buff *skb,
	       const unsigned int packet_off,
	       const unsigned int packet_len,
	       const struct ipt_p2p_info *info)
{
	unsigned char buf[9], *t;

	t = skb_header_pointer(skb, packet_off,
			       packet_len < sizeof(buf) ?
			       packet_len : sizeof(buf),
			       buf);
	if (t == NULL)
		return 0;

	if (packet_len >= 3 && memcmp(t, "GND", 3) == 0)
		return IPP2P_GNU * 100 + 51;
	if (packet_len >= 9 && memcmp(t, "GNUTELLA ", 9) == 0)
		return IPP2P_GNU * 100 + 52;
	return 0;
}

/* Search for UDP KaZaA commands */
static unsigned int
udp_search_kazaa(const struct sk_buff *skb,
		 const unsigned int packet_off,
		 const unsigned int packet_len,
		 const struct ipt_p2p_info *info)
{
	unsigned char buf[6], *t;

	if (packet_len < 6)
		return 0;

	t = skb_header_pointer(skb, packet_off + packet_len - 6, 6, buf);
	if (t == NULL)
		return 0;

	if (memcmp(t, "KaZaA\x00", 6) == 0)
		return IPP2P_KAZAA * 100 + 50;
	return 0;
}

/* Search for UDP DirectConnect commands */
static unsigned int
udp_search_directconnect(const struct sk_buff *skb,
			 const unsigned int packet_off,
			 const unsigned int packet_len,
			 const struct ipt_p2p_info *info)
{
	unsigned char hbuf[6], *head, tbuf, *tail;

	if (packet_len < 5)
		return 0;

	head = skb_header_pointer(skb, packet_off, packet_len < 7 ? 4 : 6,
				  hbuf);
	if (head == NULL)
		return 0;

	tail = skb_header_pointer(skb, packet_off + packet_len - 1, 1, &tbuf);
	if (tail == NULL)
		return 0;

	if (head[0] != 0x24)
		return 0;
	if (tail[0] != 0x7c)
		return 0;
	if (memcmp(&head[1], "SR ", 3) == 0)
		return IPP2P_DC * 100 + 60;
	if (packet_len >= 7 && memcmp(&head[1], "Ping ", 5) == 0)
		return IPP2P_DC * 100 + 61;
	return 0;
}

/* Search for UDP BitTorrent commands */
static unsigned int
udp_search_bit(const struct sk_buff *skb,
	       const unsigned int packet_off,
	       const unsigned int packet_len,
	       const struct ipt_p2p_info *info)
{
	unsigned char buf[32], *haystack;

	haystack = skb_header_pointer(skb, packet_off,
				      packet_len < sizeof(buf) ?
				      packet_len : sizeof(buf),
				      buf);
	if (haystack == NULL)
		return 0;

	switch (packet_len) {
	case 16:
		/* ^ 00 00 04 17 27 10 19 80 */
		if (get_u32(haystack, 0) == __constant_htonl(0x00000417) &&
		    get_u32(haystack, 4) == __constant_htonl(0x27101980))
			return IPP2P_BIT * 100 + 50;
		break;
	case 36:
		if (get_u32(haystack, 8) == __constant_htonl(0x00000400) &&
		    get_u32(haystack, 28) == __constant_htonl(0x00000104))
			return IPP2P_BIT * 100 + 51;
		if (get_u32(haystack, 8) == __constant_htonl(0x00000400))
			return IPP2P_BIT * 100 + 61;
		break;
	case 57:
		if (get_u32(haystack, 8) == __constant_htonl(0x00000404) &&
		    get_u32(haystack, 28) == __constant_htonl(0x00000104))
			return IPP2P_BIT * 100 + 52;
		if (get_u32(haystack, 8) == __constant_htonl(0x00000404))
			return IPP2P_BIT * 100 + 62;
		break;
	case 59:
		if (get_u32(haystack, 8) == __constant_htonl(0x00000406) &&
		    get_u32(haystack, 28) == __constant_htonl(0x00000104))
			return (IPP2P_BIT * 100 + 53);
		if (get_u32(haystack, 8) == __constant_htonl(0x00000406))
			return (IPP2P_BIT * 100 + 63);
		break;
	case 203:
		if (get_u32(haystack, 0) == __constant_htonl(0x00000405))
			return IPP2P_BIT * 100 + 54;
		break;
	case 21:
		if (get_u32(haystack, 0) == __constant_htonl(0x00000401))
			return IPP2P_BIT * 100 + 55;
		break;
	case 44:
		if (get_u32(haystack, 0)  == __constant_htonl(0x00000827) &&
		    get_u32(haystack, 4) == __constant_htonl(0x37502950))
			return IPP2P_BIT * 100 + 80;
		break;
	default:
		/* this packet does not have a constant size */
		if (packet_len >= 32 &&
		    get_u32(haystack, 8) == __constant_htonl(0x00000402) &&
		    get_u32(haystack, 28) == __constant_htonl(0x00000104))
			return IPP2P_BIT * 100 + 56;
		break;
	}

	/* some extra-bitcomet rules: "d1:" [a|r] "d2:id20:" */
	if (packet_len > 22 &&
	    get_u8(haystack, 0) == 'd' &&
	    get_u8(haystack, 1) == '1' &&
	    get_u8(haystack, 2) == ':' &&
	    (get_u8(haystack, 3) == 'a' ||
	     get_u8(haystack, 3) == 'r') &&
	    memcmp(haystack + 4, "d2:id20:", 8) == 0)
		return IPP2P_BIT * 100 + 57;

#if 0
	/* bitlord rules */
	/* packetlen must be bigger than 32 */
	/* first 4 bytes are zero */
	if (packet_len > 32 && get_u32(haystack, 0) == 0x00000000) {
		/* first rule: 00 00 00 00 01 00 00 xx xx xx xx 00 00 00 00 */
		if (get_u32(haystack, 4) == 0x00000000 &&
		    get_u32(haystack, 8) == 0x00010000 &&
		    get_u32(haystack, 16) == 0x00000000)
			return IPP2P_BIT * 100 + 71;

		/* 00 01 00 00 0d 00 00 xx xx xx xx 00 00 00 00 */
		if (get_u32(haystack, 4) == 0x00000001 &&
		    get_u32(haystack, 8) == 0x000d0000 &&
		    get_u32(haystack, 16) == 0x00000000)
			return IPP2P_BIT * 100 + 71;
	}
#endif

	return 0;
}

/* Search for Ares commands */
static unsigned int
search_ares(const struct sk_buff *skb,
	    const unsigned int poff,
	    const unsigned int plen,
	    const struct ipt_p2p_info *info)
{
	unsigned char buf[60], *payload;

	if (plen < 3)
		return 0;

	payload = skb_header_pointer(skb, poff,
				     plen < sizeof(buf) ? plen : sizeof(buf),
				     buf);
	if (payload == NULL)
		return 0;

	/* all ares packets start with  */
	if (payload[1] == 0 && plen - payload[0] == 3) {
		switch (payload[2]) {
		case 0x5a:
			/* ares connect */
			if (plen == 6 && payload[5] == 0x05)
				return IPP2P_ARES * 100 + 1;
			break;
		case 0x09:
			/*
			 * ares search, min 3 chars --> 14 bytes
			 * lets define a search can be up to 30 chars
			 * --> max 34 bytes
			 */
			if (plen >= 14 && plen <= 34)
				return IPP2P_ARES * 100 + 1;
			break;
#ifdef IPP2P_DEBUG_ARES
		default:
			printk(KERN_DEBUG "Unknown Ares command %x "
			       "recognized, len: %u\n",
			       (unsigned int)payload[2], plen);
#endif
		}
	}

#if 0
	/* found connect packet: 03 00 5a 04 03 05 */
	/* new version ares 1.8: 03 00 5a xx xx 05 */
	if (plen == 6)
		/* possible connect command */
		if (payload[0] == 0x03 && payload[1] == 0x00 &&
		    payload[2] == 0x5a && payload[5] == 0x05)
			return IPP2P_ARES * 100 + 1;

	if (plen == 60)
		/* possible download command */
		if (payload[59] == 0x0a && payload[58] == 0x0a)
			if (memcmp(t, "PUSH SHA1:", 10) == 0)
				/* found download command */
				return IPP2P_ARES * 100 + 2;
#endif

	return 0;
}

/* Search for SoulSeek commands */
static unsigned int
search_soul(const struct sk_buff *skb,
	    const unsigned int poff,
	    const unsigned int plen,
	    const struct ipt_p2p_info *info)
{
	unsigned char buf[16], *payload;

	if (plen < 8)
		return 0;

	payload = skb_header_pointer(skb, poff,
				     plen < sizeof(buf) ? plen : sizeof(buf),
				     buf);
	if (payload == NULL)
		return 0;

	/* match: xx xx xx xx | xx = sizeof(payload) - 4 */
	if (get_u32(payload, 0) == plen - 4) {
		const uint32_t m = get_u32(payload, 4);

		/* match 00 yy yy 00, yy can be everything */
		if (get_u8(payload, 4) == 0x00 && get_u8(payload, 7) == 0x00) {
#ifdef IPP2P_DEBUG_SOUL
			printk(KERN_DEBUG "0: Soulseek command 0x%x "
			       "recognized\n", get_u32(payload, 4));
#endif
			return IPP2P_SOUL * 100 + 1;
		}

		/* next match: 01 yy 00 00 | yy can be everything */
		if (get_u8(payload, 4) == 0x01 && get_u16(payload, 6) == 0x0000) {
#ifdef IPP2P_DEBUG_SOUL
			printk(KERN_DEBUG "1: Soulseek command 0x%x "
			       "recognized\n", get_u16(payload, 4));
#endif
			return IPP2P_SOUL * 100 + 2;
		}

		/* other soulseek commandos are: 1-5,7,9,13-18,22,23,26,28,35-37,40-46,50,51,60,62-69,91,92,1001 */
		/* try to do this in an intelligent way */
		/* get all small commandos */
		switch (m) {
		case 7:
		case 9:
		case 22:
		case 23:
		case 26:
		case 28:
		case 50:
		case 51:
		case 60:
		case 91:
		case 92:
		case 1001:
#ifdef IPP2P_DEBUG_SOUL
			printk(KERN_DEBUG "2: Soulseek command 0x%x "
			       "recognized\n", get_u16(payload, 4));
#endif
			return IPP2P_SOUL * 100 + 3;
		}

		if (m > 0 && m < 6) {
#ifdef IPP2P_DEBUG_SOUL
			printk(KERN_DEBUG "3: Soulseek command 0x%x "
			       "recognized\n", get_u16(payload, 4));
#endif
			return IPP2P_SOUL * 100 + 4;
		}

		if (m > 12 && m < 19) {
#ifdef IPP2P_DEBUG_SOUL
			printk(KERN_DEBUG "4: Soulseek command 0x%x "
			       "recognized\n", get_u16(payload, 4));
#endif
			return IPP2P_SOUL * 100 + 5;
		}

		if (m > 34 && m < 38) {
#ifdef IPP2P_DEBUG_SOUL
			printk(KERN_DEBUG "5: Soulseek command 0x%x "
			       "recognized\n", get_u16(payload, 4));
#endif
			return IPP2P_SOUL * 100 + 6;
		}

		if (m > 39 && m < 47) {
#ifdef IPP2P_DEBUG_SOUL
			printk(KERN_DEBUG "6: Soulseek command 0x%x "
			       "recognized\n", get_u16(payload, 4));
#endif
			return IPP2P_SOUL * 100 + 7;
		}

		if (m > 61 && m < 70) {
#ifdef IPP2P_DEBUG_SOUL
			printk(KERN_DEBUG "7: Soulseek command 0x%x "
			       "recognized\n", get_u16(payload, 4));
#endif
			return IPP2P_SOUL * 100 + 8;
		}

#ifdef IPP2P_DEBUG_SOUL
		printk(KERN_DEBUG "unknown SOULSEEK command: 0x%x, first "
		       "16 bit: 0x%x, first 8 bit: 0x%x ,soulseek ???\n",
		       get_u32(payload, 4), get_u16(payload, 4) >> 16,
		       get_u8(payload, 4) >> 24);
#endif
	}

	/* match 14 00 00 00 01 yy 00 00 00 STRING(YY) 01 00 00 00 00 46|50 00 00 00 00 */
	/* without size at the beginning! */
	if (get_u32(payload, 0) == 0x14 && get_u8(payload, 4) == 0x01) {
		uint32_t y = get_u32(payload, 5);
		const unsigned char *w;
		unsigned int off, len;

		/* we need 19 chars + string */
		if (plen < y + 19)
			return 0;
		off = poff + y + 9;
		len = plen - y + 9;
		w = skb_header_pointer(skb, off,
				       len < sizeof(buf) ? len : sizeof(buf),
				       buf);
		if (w == NULL)
			return 0;

		if (get_u32(w, 0) == 0x01 &&
		    (get_u16(w, 4) == 0x4600 ||
		     get_u16(w, 4) == 0x5000) &&
		    get_u32(w, 6) == 0x00) {
#ifdef IPP2P_DEBUG_SOUL
			printk(KERN_DEBUG "Soulseek special client command recognized\n");
#endif
			return IPP2P_SOUL * 100 + 9;
		}
	}
	return 0;
}

/* Search for WinMX commands */
static unsigned int
search_winmx(const struct sk_buff *skb,
	     const unsigned int poff,
	     const unsigned int plen,
	     const struct ipt_p2p_info *info)
{
	unsigned char buf[149], *payload;
	uint16_t start = poff;

	payload = skb_header_pointer(skb, poff,
				     plen < sizeof(buf) ? plen : sizeof(buf),
				     buf);
	if (payload == NULL)
		return 0;

	if (plen == 4 && memcmp(payload, "SEND", 4) == 0)
		return IPP2P_WINMX * 100 + 1;
	if (plen == 3 && memcmp(payload, "GET", 3) == 0)
		return IPP2P_WINMX * 100 + 2;
	/*
	if (packet_len < head_len + 10)
		return 0;
	*/
	if (plen < 10)
		return 0;

	if (memcmp(payload, "SEND", 4) == 0)
		start += 4;
	else if (memcmp(payload, "GET", 3) == 0)
		start += 3;

	if (start > poff) {
		uint8_t count = 0;

		do {
			unsigned int pos;

			pos = skb_find_text((struct sk_buff *)skb, start,
					    skb->len, info->ts_conf_winmx);
			if (pos == UINT_MAX)
				break;

			count++;
			if (count >= 2)
				return IPP2P_WINMX * 100 + 3;

			start = pos + 2;
		} while (start < skb->len);
	}

	if (plen == 149 && payload[0] == '8') {
#ifdef IPP2P_DEBUG_WINMX
		printk(KERN_INFO "maybe WinMX\n");
#endif
		if (get_u32(payload, 17) == 0 && get_u32(payload, 21) == 0 &&
		    get_u32(payload, 25) == 0 &&
//		    get_u32(payload, 33) == __constant_htonl(0x71182b1a) &&
//		    get_u32(payload, 37) == __constant_htonl(0x05050000) &&
//		    get_u32(payload, 133) == __constant_htonl(0x31097edf) &&
//		    get_u32(payload, 145) == __constant_htonl(0xdcb8f792))
		    get_u16(payload, 39) == 0 &&
		    get_u16(payload, 135) == __constant_htons(0x7edf) &&
		    get_u16(payload,147) == __constant_htons(0xf792))
		{
#ifdef IPP2P_DEBUG_WINMX
			printk(KERN_INFO "got WinMX\n");
#endif
			return IPP2P_WINMX * 100 + 4;
		}
	}
	return 0;
}

/* Search for appleJuice commands */
static unsigned int
search_apple(const struct sk_buff *skb,
	     const unsigned int poff,
	     const unsigned int plen,
	     const struct ipt_p2p_info *info)
{
	unsigned char buf[8], *payload;

	if (plen < 8)
		return 0;

	payload = skb_header_pointer(skb, poff,
				     plen < sizeof(buf) ? plen : sizeof(buf),
				     buf);
	if (payload == NULL)
		return 0;

	if (memcmp(payload, "ajprot\r\n", 8) == 0)
		return IPP2P_APPLE * 100;
	return 0;
}

/* Search for BitTorrent commands */
static unsigned int
search_bittorrent(const struct sk_buff *skb,
		  const unsigned int poff,
		  const unsigned int plen,
		  const struct ipt_p2p_info *info)
{
	unsigned char buf[20], *payload;
	unsigned int pos;

	payload = skb_header_pointer(skb, poff,
				     plen < sizeof(buf) ? plen : sizeof(buf),
				     buf);
	if (payload == NULL)
		return 0;

	/*
	 * bitcomet encrypts the first packet, so we have to detect another one
	 * later in the flow.
	 */
	if (plen == 17 &&
	    get_u32(payload, 0) == __constant_htonl(0x0d) &&
	    payload[4] == 0x06 &&
	    get_u32(payload,13) == __constant_htonl(0x4000))
		return IPP2P_BIT * 100 + 3;
	if (plen <= 20)
		return 0;

	/* test for match 0x13+"BitTorrent protocol" */
	if (payload[0] == 0x13)
		if (memcmp(payload + 1, "BitTorrent protocol", 19) == 0)
			return IPP2P_BIT * 100;
	/*
	 * Any tracker command starts with GET / then *may be* some file
	 * on web server (e.g. announce.php or dupa.pl or whatever.cgi
	 * or NOTHING for tracker on root dir) but *must have* one (or
	 * more) of strings listed below (true for scrape and announce)
	 */
	if (memcmp(payload, "GET /", 5) != 0)
		return 0;

	pos = skb_find_text((struct sk_buff *)skb, poff + 5, skb->len,
			    info->ts_conf_bt_info_hash);
	if (pos != UINT_MAX)
		return IPP2P_BIT * 100 + 1;

	pos = skb_find_text((struct sk_buff *)skb, poff + 5, skb->len,
			    info->ts_conf_bt_peer_id);
	if (pos != UINT_MAX)
		return IPP2P_BIT * 100 + 2;

	pos = skb_find_text((struct sk_buff *)skb, poff + 5, skb->len,
			    info->ts_conf_bt_passkey);
	if (pos != UINT_MAX)
		return IPP2P_BIT * 100 + 4;
	return 0;
}

/* check for Kazaa get command */
static unsigned int
search_kazaa(const struct sk_buff *skb,
	     const unsigned int poff,
	     const unsigned int plen,
	     const struct ipt_p2p_info *info)
{
	unsigned char hbuf[11], *head, tbuf[2], *tail;

	if (plen < 13)
		return 0;

	head = skb_header_pointer(skb, poff, 11, hbuf);
	if (head == NULL)
		return 0;

	tail = skb_header_pointer(skb, poff + plen - 2, 2, tbuf);
	if (tail == NULL)
		return 0;

	if (iscrlf(tail) && memcmp(head, "GET /.hash=", 11) == 0)
		return IPP2P_DATA_KAZAA * 100;

	return 0;
}

/* check for Gnutella get command */
static unsigned int
search_gnu(const struct sk_buff *skb,
	   const unsigned int poff,
	   const unsigned int plen,
	   const struct ipt_p2p_info *info)
{
	unsigned char hbuf[15], *head, tbuf[2], *tail;

	if (plen < 11)
		return 0;

	head = skb_header_pointer(skb, poff,
				  plen - 2 < sizeof(hbuf) ?
				  plen - 2 : sizeof(hbuf),
				  hbuf);
	if (head == NULL)
		return 0;

	tail = skb_header_pointer(skb, poff + plen - 2, 2, tbuf);
	if (tail == NULL)
		return 0;

	if (!iscrlf(tail))
		return 0;
	if (memcmp(head, "GET /get/", 9) == 0)
		return IPP2P_DATA_GNU * 100 + 1;
	if (plen >= 15 && memcmp(head, "GET /uri-res/", 13) == 0)
		return IPP2P_DATA_GNU * 100 + 2;
	return 0;
}

/* check for Gnutella get commands and other typical data */
static unsigned int
search_all_gnu(const struct sk_buff *skb,
	       const unsigned int poff,
	       const unsigned int plen,
	       const struct ipt_p2p_info *info)
{
	unsigned char hbuf[17], *head, tbuf[2], *tail;
	unsigned int off, pos;

	if (plen < 11)
		return 0;

	head = skb_header_pointer(skb, poff,
				  plen - 2 < sizeof(hbuf) ?
				  plen - 2 : sizeof(hbuf),
				  hbuf);
	if (head == NULL)
		return 0;

	tail = skb_header_pointer(skb, poff + plen - 2, 2, tbuf);
	if (tail == NULL)
		return 0;

	if (!iscrlf(tail))
		return 0;

	if (plen >= 19 && memcmp(head, "GNUTELLA CONNECT/", 17) == 0)
		return IPP2P_GNU * 100 + 1;

	if (memcmp(head, "GNUTELLA/", 9) == 0)
		return IPP2P_GNU * 100 + 2;
	if (plen < 22)
		return 0;
	if (memcmp(head, "GET /get/", 9) == 0)
		off = 9;
	else if (memcmp(head, "GET /uri-res/", 13) == 0)
		off = 13;
	else
		return 0;

	pos = skb_find_text((struct sk_buff *)skb, poff + off, skb->len,
			    info->ts_conf_gnu_x_gnutella);
	if (pos != UINT_MAX)
		return IPP2P_GNU * 100 + 3;

	pos = skb_find_text((struct sk_buff *)skb, poff + off, skb->len,
			    info->ts_conf_gnu_x_queue);

	if (pos != UINT_MAX)
		return IPP2P_GNU * 100 + 3;
	return 0;
}

/* check for KaZaA download commands and other typical data */
/* plen is guaranteed to be >= 5 (see @matchlist) */
static unsigned int
search_all_kazaa(const struct sk_buff *skb,
		 const unsigned int poff,
		 const unsigned int plen,
		 const struct ipt_p2p_info *info)
{
	unsigned char hbuf[5], *head, tbuf[2], *tail;
	unsigned int pos;

	if (plen < 7)
		/* too short for anything we test for - early bailout */
		return 0;
	head = skb_header_pointer(skb, poff, sizeof(hbuf), hbuf);
	if (head == NULL)
		return 0;

	tail = skb_header_pointer(skb, poff + plen - 2, 2, tbuf);
	if (tail == NULL)
		return 0;

	if (!iscrlf(tail))
		return 0;

	if (memcmp(head, "GIVE ", 5) == 0)
		return IPP2P_KAZAA * 100 + 1;

	if (memcmp(head, "GET /", 5) != 0)
		return 0;

	if (plen < 18)
		/* The next tests would not succeed anyhow. */
		return 0;

	pos = skb_find_text((struct sk_buff *)skb, poff + 5, skb->len,
			    info->ts_conf_kz_x_kazaa_username);
	if (pos != UINT_MAX)
		return IPP2P_KAZAA * 100 + 2;

	pos = skb_find_text((struct sk_buff *)skb, poff + 5, skb->len,
			    info->ts_conf_kz_user_agent);
	if (pos != UINT_MAX)
		return IPP2P_KAZAA * 100 + 2;

	return 0;
}

/* fast check for eDonkey file segment transfer command */
static unsigned int
search_edk(const struct sk_buff *skb,
	   const unsigned int poff,
	   const unsigned int plen,
	   const struct ipt_p2p_info *info)
{
	unsigned char buf[6], *payload;

	if (plen < 6)
		return 0;

	payload = skb_header_pointer(skb, poff, sizeof(buf), buf);
	if (payload == NULL)
		return 0;

	if (payload[0] != 0xe3)
		return 0;
	if (payload[5] == 0x47)
		return IPP2P_DATA_EDK * 100;
	return 0;
}

/* intensive but slower search for some eDonkey packets including size check */
static unsigned int
search_all_edk(const struct sk_buff *skb,
	       const unsigned int poff,
	       const unsigned int plen,
	       const struct ipt_p2p_info *info)
{
	unsigned char buf[6], *payload;
	unsigned int cmd;

	if (plen < 6)
		return 0;

	payload = skb_header_pointer(skb, poff, sizeof(buf), buf);
	if (payload == NULL)
		return 0;

	if (payload[0] != 0xe3)
		return 0;

	cmd = get_u16(payload, 1);
	if (cmd == plen - 5) {
		switch (payload[5]) {
		case 0x01:
			/* Client: hello or Server:hello */
			return IPP2P_EDK * 100 + 1;
		case 0x4c:
			/* Client: Hello-Answer */
			return IPP2P_EDK * 100 + 9;
		}
	}
	return 0;
}

/* fast check for Direct Connect send command */
static unsigned int
search_dc(const struct sk_buff *skb,
	  const unsigned int poff,
	  const unsigned int plen,
	  const struct ipt_p2p_info *info)
{
	unsigned char buf[6], *payload;

	if (plen < 6)
		return 0;

	payload = skb_header_pointer(skb, poff, sizeof(buf), buf);
	if (payload == NULL)
		return 0;

	if (payload[0] != 0x24)
		return 0;
	if (memcmp(&payload[1], "Send|", 5) == 0)
		return IPP2P_DATA_DC * 100;
	return 0;
}

/* intensive but slower check for all direct connect packets */
static unsigned int
search_all_dc(const struct sk_buff *skb,
	      const unsigned int poff,
	      const unsigned int plen,
	      const struct ipt_p2p_info *info)
{
	unsigned char hbuf[8], *head, tbuf, *tail;
	const unsigned char *t;

	if (plen < 7)
		return 0;
	head = skb_header_pointer(skb, poff,
				  plen - 1 < sizeof(hbuf) ?
				  plen - 1 : sizeof(hbuf),
				  hbuf);
	if (head == NULL)
		return 0;
	tail = skb_header_pointer(skb, poff + plen - 1, 1, &tbuf);
	if (tail == NULL)
		return 0;
	if (head[0] != 0x24)
		return 0;
	if (tail[0] != 0x7c)
		return 0;
	t = &head[1];
	/* Client-Hub-Protocol */
	if (memcmp(t, "Lock ", 5) == 0)
		return IPP2P_DC * 100 + 1;
	/*
	 * Client-Client-Protocol, some are already recognized by client-hub
	 * (like lock)
	 */
	if (plen >= 9 && memcmp(t, "MyNick ", 7) == 0)
		return IPP2P_DC * 100 + 38;
	return 0;
}

/* check for mute */
static unsigned int
search_mute(const struct sk_buff *skb,
	    const unsigned int poff,
	    const unsigned int plen,
	    const struct ipt_p2p_info *info)
{
	if (plen == 209 || plen == 345 || plen == 473 || plen == 609 ||
	    plen == 1121) {
		unsigned char buf[11], *payload;

		payload = skb_header_pointer(skb, poff, sizeof(buf), buf);
		if (payload == NULL)
			return 0;

		if (memcmp(payload,"PublicKey: ", 11) == 0) {
			return IPP2P_MUTE * 100 + 0;
		}
	}
	return 0;
}

/* check for xdcc */
static unsigned int
search_xdcc(const struct sk_buff *skb,
	    const unsigned int poff,
	    const unsigned int plen,
	    const struct ipt_p2p_info *info)
{
	unsigned char hbuf[8], *head, tbuf[2], *tail;
	unsigned int pos;

	/* search in small packets only */
	if (plen <= 20 || plen >= 200)
		return 0;
	head = skb_header_pointer(skb, poff,
				  plen - 2 < sizeof(hbuf) ?
				  plen - 2 : sizeof(hbuf),
				  hbuf);
	if (head == NULL)
		return 0;
	tail = skb_header_pointer(skb, poff + plen - 2, 2, &tbuf);
	if (tail == NULL)
		return 0;
	if (memcmp(head, "PRIVMSG ", 8) != 0 || !iscrlf(tail))
		return 0;
	/*
	 * It seems to be an IRC private message, check for xdcc command
	 */
	pos = skb_find_text((struct sk_buff *)skb, poff + 8, skb->len,
			    info->ts_conf_xdcc);
	if (pos != UINT_MAX)
		return IPP2P_XDCC * 100 + 0;

	return 0;
}

/* search for waste */
static unsigned int
search_waste(const struct sk_buff *skb,
	     const unsigned int poff,
	     const unsigned int plen,
	     const struct ipt_p2p_info *info)
{
	unsigned char buf[9], *payload;

	if (plen < 9)
		return 0;

	payload = skb_header_pointer(skb, poff,
				     plen < sizeof(buf) ? plen : sizeof(buf),
				     buf);
	if (payload == NULL)
		return 0;

	if (memcmp(payload, "GET.sha1:", 9) == 0)
		return IPP2P_WASTE * 100 + 0;

	return 0;
}

static const struct {
	unsigned int command;
	unsigned int packet_len;
	unsigned int (*function_name)(const struct sk_buff *,
				      const unsigned int,
				      const unsigned int,
				      const struct ipt_p2p_info *);
} matchlist[] = {
	{IPP2P_EDK,         20, search_all_edk},
	{IPP2P_DATA_KAZAA, 200, search_kazaa}, /* exp */
	{IPP2P_DATA_EDK,    60, search_edk}, /* exp */
	{IPP2P_DATA_DC,     26, search_dc}, /* exp */
	{IPP2P_DC,           5, search_all_dc},
	{IPP2P_DATA_GNU,    40, search_gnu}, /* exp */
	{IPP2P_GNU,          5, search_all_gnu},
	{IPP2P_KAZAA,        5, search_all_kazaa},
	{IPP2P_BIT,         20, search_bittorrent},
	{IPP2P_APPLE,        5, search_apple},
	{IPP2P_SOUL,         5, search_soul},
	{IPP2P_WINMX,        2, search_winmx},
	{IPP2P_ARES,         5, search_ares},
	{IPP2P_MUTE,       200, search_mute},
	{IPP2P_WASTE,        5, search_waste},
	{IPP2P_XDCC,         5, search_xdcc},
	{0},
};

static const struct {
	unsigned int command;
	unsigned int packet_len;
	unsigned int (*function_name)(const struct sk_buff *,
				      const unsigned int,
				      const unsigned int,
				      const struct ipt_p2p_info *);
} udp_list[] = {
	{IPP2P_KAZAA, 14, udp_search_kazaa},
	{IPP2P_BIT,   23, udp_search_bit},
	{IPP2P_GNU,   11, udp_search_gnu},
	{IPP2P_EDK,    9, udp_search_edk},
	{IPP2P_DC,    12, udp_search_directconnect},
	{0},
};

static void
ipp2p_print_result_tcp4(const union nf_inet_addr *saddr, short sport,
                        const union nf_inet_addr *daddr, short dport,
                        bool p2p_result, unsigned int hlen)
{
	printk("IPP2P.debug:TCP-match: %d from: %pI4:%hu to: %pI4:%hu Length: %u\n",
	       p2p_result, &saddr->ip, sport, &daddr->ip, dport, hlen);
}

static void
ipp2p_print_result_tcp6(const union nf_inet_addr *saddr, short sport,
                        const union nf_inet_addr *daddr, short dport,
                        bool p2p_result, unsigned int hlen)
{
	printk("IPP2P.debug:TCP-match: %d from: %pI6:%hu to: %pI6:%hu Length: %u\n",
	       p2p_result, &saddr->in6, sport, &daddr->in6, dport, hlen);
}

static bool
ipp2p_mt_tcp(const struct ipt_p2p_info *info, const struct tcphdr *tcph,
	     const struct sk_buff *skb, unsigned int packet_off,
	     unsigned int packet_len,
	     const struct ipp2p_result_printer *rp)
{
	size_t tcph_len = tcph->doff * 4;
	int i;

	if (tcph->fin) return 0;  /* if FIN bit is set bail out */
	if (tcph->syn) return 0;  /* if SYN bit is set bail out */
	if (tcph->rst) return 0;  /* if RST bit is set bail out */

	if (packet_len < tcph_len) {
		if (info->debug)
			pr_info("TCP header indicated packet larger than it is\n");
		return 0;
	}
	if (packet_len == tcph_len)
		return 0;

	packet_off += tcph_len;
	packet_len -= tcph_len;

	for (i = 0; matchlist[i].command; ++i) {
		if ((info->cmd & matchlist[i].command) != matchlist[i].command)
			continue;
		if (packet_len <= matchlist[i].packet_len)
			continue;
		if (matchlist[i].function_name(skb, packet_off, packet_len,
					       info)) {
			if (info->debug)
				print_result(rp, true, packet_len);
			return true;
		}
	}
	return false;
}

static void
ipp2p_print_result_udp4(const union nf_inet_addr *saddr, short sport,
                        const union nf_inet_addr *daddr, short dport,
                        bool p2p_result, unsigned int hlen)
{
	printk("IPP2P.debug:UDP-match: %d from: %pI4:%hu to: %pI4:%hu Length: %u\n",
	       p2p_result, &saddr->ip, sport, &daddr->ip, dport, hlen);
}

static void
ipp2p_print_result_udp6(const union nf_inet_addr *saddr, short sport,
                        const union nf_inet_addr *daddr, short dport,
                        bool p2p_result, unsigned int hlen)
{
	printk("IPP2P.debug:UDP-match: %d from: %pI6:%hu to: %pI6:%hu Length: %u\n",
	       p2p_result, &saddr->in6, sport, &daddr->in6, dport, hlen);
}

static bool
ipp2p_mt_udp(const struct ipt_p2p_info *info, const struct udphdr *udph,
	     const struct sk_buff *skb, unsigned int packet_off,
	     unsigned int packet_len,
	     const struct ipp2p_result_printer *rp)
{
	size_t udph_len = sizeof(*udph);
	int i;

	if (packet_len < udph_len) {
		if (info->debug)
			pr_info("UDP header indicated packet larger than it is\n");
		return 0;
	}
	if (packet_len == udph_len)
		return 0;

	packet_off += udph_len;
	packet_len -= udph_len;

	for (i = 0; udp_list[i].command; ++i) {
		if ((info->cmd & udp_list[i].command) != udp_list[i].command)
			continue;
		if (packet_len <= udp_list[i].packet_len)
			continue;
		if (udp_list[i].function_name(skb, packet_off, packet_len,
					      info)) {
			if (info->debug)
				print_result(rp, true, packet_len);
			return true;
		}
	}
	return false;
}

static bool
ipp2p_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
	const struct ipt_p2p_info *info = par->matchinfo;
	struct ipp2p_result_printer printer;
	union nf_inet_addr saddr, daddr;
	uint8_t family = xt_family(par);
	unsigned int packet_len;
	int protocol;

	/*
	 * must not be a fragment
	 *
	 * NB, `par->fragoff` may be zero for a fragmented IPv6 packet.
	 * However, in that case the later call to `ipv6_find_hdr` will not find
	 * a transport protocol, and so we will return 0 there.
	 */
	if (par->fragoff != 0) {
		if (info->debug)
			printk("IPP2P.match: offset found %d\n", par->fragoff);
		return 0;
	}

	if (family == NFPROTO_IPV4) {
		const struct iphdr *ip = ip_hdr(skb);

		saddr.ip = ip->saddr;
		daddr.ip = ip->daddr;
		protocol = ip->protocol;
		packet_len = ip_transport_len(skb);
	} else {
		const struct ipv6hdr *ip = ipv6_hdr(skb);
		int thoff = 0;

		saddr.in6 = ip->saddr;
		daddr.in6 = ip->daddr;
		protocol = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
		if (protocol < 0)
			return 0;
		packet_len = ipv6_transport_len(skb);
	}

	printer.saddr = &saddr;
	printer.daddr = &daddr;

	switch (protocol) {
	case IPPROTO_TCP:	/* what to do with a TCP packet */
	{
		const struct tcphdr *tcph;
		struct tcphdr _tcph;

		tcph = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph);
		if (tcph == NULL)
			return 0;

		printer.sport = ntohs(tcph->source);
		printer.dport = ntohs(tcph->dest);
		printer.print = family == NFPROTO_IPV6 ?
		                ipp2p_print_result_tcp6 : ipp2p_print_result_tcp4;

		return ipp2p_mt_tcp(info, tcph, skb, par->thoff, packet_len,
				    &printer);
	}
	case IPPROTO_UDP:	/* what to do with a UDP packet */
	case IPPROTO_UDPLITE:
	{
		const struct udphdr *udph;
		struct udphdr _udph;

		udph = skb_header_pointer(skb, par->thoff, sizeof(_udph), &_udph);
		if (udph == NULL)
			return 0;

		printer.sport = ntohs(udph->source);
		printer.dport = ntohs(udph->dest);
		printer.print = family == NFPROTO_IPV6 ?
		                ipp2p_print_result_udp6 : ipp2p_print_result_udp4;

		return ipp2p_mt_udp(info, udph, skb, par->thoff, packet_len,
				    &printer);
	}
	default:
		return 0;
	}
}

static int ipp2p_mt_check(const struct xt_mtchk_param *par)
{
	struct ipt_p2p_info *info = par->matchinfo;
	struct ts_config *ts_conf;

	ts_conf = textsearch_prepare(TEXTSEARCH_ALGO, "\x20\x22", 2,
				     GFP_KERNEL, TS_AUTOLOAD);
	if (IS_ERR(ts_conf))
		goto err_return;
	info->ts_conf_winmx = ts_conf;

	ts_conf = textsearch_prepare(TEXTSEARCH_ALGO, "info_hash=", 10,
				     GFP_KERNEL, TS_AUTOLOAD);
	if (IS_ERR(ts_conf))
		goto err_ts_destroy_winmx;
	info->ts_conf_bt_info_hash = ts_conf;

	ts_conf = textsearch_prepare(TEXTSEARCH_ALGO, "peer_id=", 8,
				     GFP_KERNEL, TS_AUTOLOAD);
	if (IS_ERR(ts_conf))
		goto err_ts_destroy_bt_info_hash;
	info->ts_conf_bt_peer_id = ts_conf;

	ts_conf = textsearch_prepare(TEXTSEARCH_ALGO, "passkey", 8,
				     GFP_KERNEL, TS_AUTOLOAD);
	if (IS_ERR(ts_conf))
		goto err_ts_destroy_bt_peer_id;
	info->ts_conf_bt_passkey = ts_conf;

	ts_conf = textsearch_prepare(TEXTSEARCH_ALGO, "\r\nX-Gnutella-", 13,
				     GFP_KERNEL, TS_AUTOLOAD);
	if (IS_ERR(ts_conf))
		goto err_ts_destroy_bt_passkey;
	info->ts_conf_gnu_x_gnutella = ts_conf;

	ts_conf = textsearch_prepare(TEXTSEARCH_ALGO, "\r\nX-Queue-", 10,
				     GFP_KERNEL, TS_AUTOLOAD);
	if (IS_ERR(ts_conf))
		goto err_ts_destroy_gnu_x_gnutella;
	info->ts_conf_gnu_x_queue = ts_conf;

	ts_conf = textsearch_prepare(TEXTSEARCH_ALGO,
				     "\r\nX-Kazaa-Username: ", 20,
				     GFP_KERNEL, TS_AUTOLOAD);
	if (IS_ERR(ts_conf))
		goto err_ts_destroy_gnu_x_queue;
	info->ts_conf_kz_x_kazaa_username = ts_conf;

	ts_conf = textsearch_prepare(TEXTSEARCH_ALGO,
				     "\r\nUser-Agent: PeerEnabler/", 26,
				     GFP_KERNEL, TS_AUTOLOAD);
	if (IS_ERR(ts_conf))
		goto err_ts_destroy_kazaa_x_kazaa_username;
	info->ts_conf_kz_user_agent = ts_conf;

	ts_conf = textsearch_prepare(TEXTSEARCH_ALGO, ":xdcc send #", 12,
				     GFP_KERNEL, TS_AUTOLOAD);
	if (IS_ERR(ts_conf))
		goto err_ts_destroy_kazaa_user_agent;
	info->ts_conf_xdcc = ts_conf;

	return 0;

err_ts_destroy_kazaa_user_agent:
	textsearch_destroy(info->ts_conf_kz_user_agent);

err_ts_destroy_kazaa_x_kazaa_username:
	textsearch_destroy(info->ts_conf_kz_x_kazaa_username);

err_ts_destroy_gnu_x_queue:
	textsearch_destroy(info->ts_conf_gnu_x_queue);

err_ts_destroy_gnu_x_gnutella:
	textsearch_destroy(info->ts_conf_gnu_x_gnutella);

err_ts_destroy_bt_passkey:
	textsearch_destroy(info->ts_conf_bt_passkey);

err_ts_destroy_bt_peer_id:
	textsearch_destroy(info->ts_conf_bt_peer_id);

err_ts_destroy_bt_info_hash:
	textsearch_destroy(info->ts_conf_bt_info_hash);

err_ts_destroy_winmx:
	textsearch_destroy(info->ts_conf_winmx);

err_return:
	return PTR_ERR(ts_conf);
}

static void ipp2p_mt_destroy(const struct xt_mtdtor_param *par)
{
	struct ipt_p2p_info *info = (struct ipt_p2p_info *) par->matchinfo;

	textsearch_destroy(info->ts_conf_winmx);
	textsearch_destroy(info->ts_conf_bt_info_hash);
	textsearch_destroy(info->ts_conf_bt_peer_id);
	textsearch_destroy(info->ts_conf_bt_passkey);
	textsearch_destroy(info->ts_conf_gnu_x_gnutella);
	textsearch_destroy(info->ts_conf_gnu_x_queue);
	textsearch_destroy(info->ts_conf_kz_x_kazaa_username);
	textsearch_destroy(info->ts_conf_kz_user_agent);
	textsearch_destroy(info->ts_conf_xdcc);
}

static struct xt_match ipp2p_mt_reg[] __read_mostly = {
	{
		.name       = "ipp2p",
		.revision   = 1,
		.family     = NFPROTO_IPV4,
		.checkentry = ipp2p_mt_check,
		.match      = ipp2p_mt,
		.destroy    = ipp2p_mt_destroy,
		.matchsize  = sizeof(struct ipt_p2p_info),
		.me         = THIS_MODULE,
	},
	{
		.name       = "ipp2p",
		.revision   = 1,
		.family     = NFPROTO_IPV6,
		.checkentry = ipp2p_mt_check,
		.match      = ipp2p_mt,
		.destroy    = ipp2p_mt_destroy,
		.matchsize  = sizeof(struct ipt_p2p_info),
		.me         = THIS_MODULE,
	},
};

static int __init ipp2p_mt_init(void)
{
	return xt_register_matches(ipp2p_mt_reg, ARRAY_SIZE(ipp2p_mt_reg));
}

static void __exit ipp2p_mt_exit(void)
{
	xt_unregister_matches(ipp2p_mt_reg, ARRAY_SIZE(ipp2p_mt_reg));
}

module_init(ipp2p_mt_init);
module_exit(ipp2p_mt_exit);
MODULE_ALIAS("ipt_ipp2p");
MODULE_ALIAS("ip6t_ipp2p");