diff --git a/sbin/ipfw/ipfw.8 b/sbin/ipfw/ipfw.8
index ef05581b19f8..7ba90e46a94c 100644
--- a/sbin/ipfw/ipfw.8
+++ b/sbin/ipfw/ipfw.8
@@ -1236,6 +1236,12 @@ specified as argument.
 TCP packets only.
 Match if the TCP header acknowledgment number field is set to
 .Ar ack .
+.It Cm tcpdatalen Ar tcpdatalen-list
+Matches TCP packets whose length of TCP data is
+.Ar tcpdatalen-list ,
+which is either a single value or a list of values or ranges
+specified in the same way as
+.Ar ports .
 .It Cm tcpflags Ar spec
 TCP packets only.
 Match if the TCP header contains the comma separated list of
diff --git a/sbin/ipfw/ipfw2.c b/sbin/ipfw/ipfw2.c
index bfc0fc43f42b..fe3a8fe21d01 100644
--- a/sbin/ipfw/ipfw2.c
+++ b/sbin/ipfw/ipfw2.c
@@ -233,6 +233,7 @@ enum tokens {
 	TOK_IPVER,
 	TOK_ESTAB,
 	TOK_SETUP,
+	TOK_TCPDATALEN,
 	TOK_TCPFLAGS,
 	TOK_TCPOPTS,
 	TOK_TCPSEQ,
@@ -348,6 +349,7 @@ struct _s_x rule_options[] = {
 	{ "estab",		TOK_ESTAB },
 	{ "established",	TOK_ESTAB },
 	{ "setup",		TOK_SETUP },
+	{ "tcpdatalen",		TOK_TCPDATALEN },
 	{ "tcpflags",		TOK_TCPFLAGS },
 	{ "tcpflgs",		TOK_TCPFLAGS },
 	{ "tcpoptions",		TOK_TCPOPTS },
@@ -481,6 +483,7 @@ struct _s_x _port_name[] = {
 	{"iplen",	O_IPLEN},
 	{"ipttl",	O_IPTTL},
 	{"mac-type",	O_MAC_TYPE},
+	{"tcpdatalen",	O_TCPDATALEN},
 	{NULL,		0}
 };
 
@@ -1395,6 +1398,14 @@ show_ipfw(struct ip_fw *rule, int pcwidth, int bcwidth)
 				printf(" established");
 				break;
 
+			case O_TCPDATALEN:
+				if (F_LEN(cmd) == 1)
+				    printf(" tcpdatalen %u", cmd->arg1 );
+				else
+				    print_newports((ipfw_insn_u16 *)cmd, 0,
+					O_TCPDATALEN);
+				break;
+
 			case O_TCPFLAGS:
 				print_flags("tcpflags", cmd, f_tcpflags);
 				break;
@@ -2072,6 +2083,7 @@ help(void)
 "	mac ... | mac-type LIST | proto LIST | {recv|xmit|via} {IF|IPADDR} |\n"
 "	setup | {tcpack|tcpseq|tcpwin} NN | tcpflags SPEC | tcpoptions SPEC |\n"
 "	verrevpath | versrcreach | antispoof\n"
+"	tcpdatalen LIST | verrevpath | versrcreach | antispoof\n"
 );
 exit(0);
 }
@@ -3542,6 +3554,17 @@ add(int ac, char *av[])
 				(TH_SYN) | ( (TH_ACK) & 0xff) <<8 );
 			break;
 
+		case TOK_TCPDATALEN:
+			NEED1("tcpdatalen requires length");
+			if (strpbrk(*av, "-,")) {
+			    if (!add_ports(cmd, *av, 0, O_TCPDATALEN))
+				errx(EX_DATAERR, "invalid tcpdata len %s", *av);
+			} else
+			    fill_cmd(cmd, O_TCPDATALEN, 0,
+				    strtoul(*av, NULL, 0));
+			ac--; av++;
+			break;
+
 		case TOK_TCPOPTS:
 			NEED1("missing argument for tcpoptions");
 			fill_flags(cmd, O_TCPOPTS, f_tcpopts, *av);
diff --git a/sys/netinet/ip_fw.h b/sys/netinet/ip_fw.h
index 15ce84b288b5..97711899d37b 100644
--- a/sys/netinet/ip_fw.h
+++ b/sys/netinet/ip_fw.h
@@ -136,6 +136,7 @@ enum ipfw_opcodes {		/* arguments (4 byte each)	*/
 	O_JAIL,			/* u32 = id			*/
 	O_ALTQ,			/* u32 = altq classif. qid	*/
 	O_DIVERTED,		/* arg1=bitmap (1:loop, 2:out)	*/
+	O_TCPDATALEN,		/* arg1 = tcp data len		*/
 
 	O_LAST_OPCODE		/* not an opcode!		*/
 };
diff --git a/sys/netinet/ip_fw2.c b/sys/netinet/ip_fw2.c
index 854e2d927e43..c45a04f5f932 100644
--- a/sys/netinet/ip_fw2.c
+++ b/sys/netinet/ip_fw2.c
@@ -2203,6 +2203,28 @@ ipfw_chk(struct ip_fw_args *args)
 				    flags_match(cmd, ip->ip_tos));
 				break;
 
+			case O_TCPDATALEN:
+				if (proto == IPPROTO_TCP && offset == 0) {
+				    struct tcphdr *tcp;
+				    uint16_t x;
+				    uint16_t *p;
+				    int i;
+
+				    tcp = L3HDR(struct tcphdr,ip);
+				    x = ip_len -
+					((ip->ip_hl + tcp->th_off) << 2);
+				    if (cmdlen == 1) {
+					match = (cmd->arg1 == x);
+					break;
+				    }
+				    /* otherwise we have ranges */
+				    p = ((ipfw_insn_u16 *)cmd)->ports;
+				    i = cmdlen - 1;
+				    for (; !match && i>0; i--, p += 2)
+					match = (x >= p[0] && x <= p[1]);
+				}
+				break;
+
 			case O_TCPFLAGS:
 				match = (proto == IPPROTO_TCP && offset == 0 &&
 				    flags_match(cmd,
@@ -3014,6 +3036,7 @@ check_ipfw_struct(struct ip_fw *rule, int size)
 		case O_IPID:
 		case O_IPTTL:
 		case O_IPLEN:
+		case O_TCPDATALEN:
 			if (cmdlen < 1 || cmdlen > 31)
 				goto bad_size;
 			break;