o) Restructure tcpdrop(8) to provide a facility to try to drop all established

   connections.  Including a flag to instead output a sequence of tcpdrop(8)
   invocations that would accomplish the same thing, which is convenient for
   scripting.
o) Make tcpdrop complain if the addresses given to it are entirely in different
   address families, rather than failing silently.
o) When cross-referencing httpd(8), do not explicitly specify the apache2 port,
   since the example in question is generic.

2 files changed, 319 insertions, 56 deletions

diff --git a/usr.sbin/tcpdrop/tcpdrop.8 b/usr.sbin/tcpdrop/tcpdrop.8
index 5fd3a43..b846257 100644
--- a/usr.sbin/tcpdrop/tcpdrop.8
+++ b/usr.sbin/tcpdrop/tcpdrop.8
@@ -1,5 +1,6 @@
 .\"	$OpenBSD: tcpdrop.8,v 1.5 2004/05/24 13:57:31 jmc Exp $
 .\"
+.\" Copyright (c) 2009 Juli Mallett <jmallett@FreeBSD.org>
 .\" Copyright (c) 2004 Markus Friedl <markus@openbsd.org>
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
@@ -16,35 +17,58 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd March 21, 2004
+.Dd March 24, 2009
 .Dt TCPDROP 8
 .Os
 .Sh NAME
 .Nm tcpdrop
-.Nd drop a TCP connection
+.Nd drop TCP connections
 .Sh SYNOPSIS
 .Nm tcpdrop
-.Ar laddr
-.Ar lport
-.Ar faddr
-.Ar fport
+.Ar local-address
+.Ar local-port
+.Ar foreign-address
+.Ar foreign-port
+.Nm tcpdrop
+.Op Fl l
+.Fl a
 .Sh DESCRIPTION
 The
 .Nm
-command drops the TCP connection specified by the local address
-.Ar laddr ,
+command may be used to drop TCP connections from the command line.
+.Pp
+If
+.Fl a
+is specified then
+.Nm
+will attempt to drop all active connections.
+The
+.Fl l
+flag may be given to list the tcpdrop invocation to drop all active
+connections one at a time.
+.Pp
+If
+.Fl a
+is not specified then only the connection between the given local
+address
+.Ar local-address ,
 port
-.Ar lport
+.Ar local-port ,
 and the foreign address
-.Ar faddr ,
+.Ar foreign-address ,
 port
-.Ar fport .
-Addresses and ports can be specified by name or numeric value.
+.Ar foreign-port ,
+will be dropped.
+.Pp
+Addresses and ports may be specified by name or numeric value.
+Both IPv4 and IPv6 address formats are supported.
+.Nm
+in case of success or failure.
 .Sh EXIT STATUS
 .Ex -std
 .Sh EXAMPLES
 If a connection to
-.Xr httpd 8 Pq Pa ports/www/apache2
+.Xr httpd 8
 is causing congestion on a network link, one can drop the TCP session
 in charge:
 .Bd -literal -offset indent
@@ -57,8 +81,16 @@ The following command will drop the connection:
 .Bd -literal -offset indent
 # tcpdrop 192.168.5.41 80 192.168.5.1 26747
 .Ed
+.Pp
+The following command will drop all connections but those to or from
+port 22, the port used by
+.Xr sshd 8 :
+.Bd -literal -offset indent
+# tcpdrop -l -a | grep -vw 22 | sh
+.Ed
 .Sh SEE ALSO
 .Xr netstat 1 ,
 .Xr sockstat 1
 .Sh AUTHORS
 .An Markus Friedl Aq markus@openbsd.org
+.An Juli Mallett Aq jmallett@FreeBSD.org
diff --git a/usr.sbin/tcpdrop/tcpdrop.c b/usr.sbin/tcpdrop/tcpdrop.c
index 06ca0da..6aae85c 100644
--- a/usr.sbin/tcpdrop/tcpdrop.c
+++ b/usr.sbin/tcpdrop/tcpdrop.c
@@ -1,6 +1,7 @@
 /* $OpenBSD: tcpdrop.c,v 1.4 2004/05/22 23:55:22 deraadt Exp $ */
 
 /*-
+ * Copyright (c) 2009 Juli Mallett <jmallett@FreeBSD.org>
  * Copyright (c) 2004 Markus Friedl <markus@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
@@ -21,15 +22,41 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/types.h>
 #include <sys/socket.h>
+#include <sys/socketvar.h>
 #include <sys/sysctl.h>
 #include <netinet/in.h>
+
+#include <netinet/in_pcb.h>
+#define TCPSTATES
+#include <netinet/tcp_fsm.h>
 #include <netinet/tcp_var.h>
 
 #include <err.h>
 #include <netdb.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
+
+#define	TCPDROP_FOREIGN		0
+#define	TCPDROP_LOCAL		1
+
+struct host_service {
+	char hs_host[NI_MAXHOST];
+	char hs_service[NI_MAXSERV];
+};
+
+static bool tcpdrop_list_commands = false;
+
+static struct xinpgen *getxpcblist(const char *);
+static void sockinfo(const struct sockaddr *, struct host_service *);
+static bool tcpdrop(const struct sockaddr *, const struct sockaddr *);
+static bool tcpdropall(void);
+static bool tcpdropbyname(const char *, const char *, const char *,
+    const char *);
+static bool tcpdropconn(const struct in_conninfo *);
+static void usage(void);
 
 /*
  * Drop a tcp connection.
@@ -37,55 +64,259 @@ __FBSDID("$FreeBSD$");
 int
 main(int argc, char *argv[])
 {
-	struct addrinfo hints, *ail, *aif, *laddr, *faddr;
-	/* addrs[0] is a foreign socket, addrs[1] is a local one. */
-	struct sockaddr_storage addrs[2];
-	int mib[] = { CTL_NET, PF_INET, IPPROTO_TCP, TCPCTL_DROP };
-	int gaierr, rval = 0;
-	char fhbuf[NI_MAXHOST], fsbuf[NI_MAXSERV], lhbuf[NI_MAXHOST],
-	    lsbuf[NI_MAXSERV];
+	bool dropall;
+	int ch;
+
+	dropall = false;
+
+	while ((ch = getopt(argc, argv, "al")) != -1) {
+		switch (ch) {
+		case 'a':
+			dropall = true;
+			break;
+		case 'l':
+			tcpdrop_list_commands = true;
+			break;
+		default:
+			usage();
+		}
+	}
+	argc -= optind;
+	argv += optind;
+
+	if (dropall) {
+		if (argc != 0)
+			usage();
+		if (!tcpdropall())
+			exit(1);
+		exit(0);
+	}
 
-	if (argc != 5) {
-		fprintf(stderr, "usage: tcpdrop laddr lport faddr fport\n");
+	if (argc != 4 || tcpdrop_list_commands)
+		usage();
+
+	if (!tcpdropbyname(argv[0], argv[1], argv[2], argv[3]))
 		exit(1);
+
+	exit(0);
+}
+
+static struct xinpgen *
+getxpcblist(const char *name)
+{
+	struct xinpgen *xinp;
+	size_t len;
+	int rv;
+
+	len = 0;
+	rv = sysctlbyname(name, NULL, &len, NULL, 0);
+	if (rv == -1)
+		err(1, "sysctlbyname %s", name);
+
+	if (len == 0)
+		errx(1, "%s is empty", name);
+
+	xinp = malloc(len);
+	if (xinp == NULL)
+		errx(1, "malloc failed");
+
+	rv = sysctlbyname(name, xinp, &len, NULL, 0);
+	if (rv == -1)
+		err(1, "sysctlbyname %s", name);
+
+	return (xinp);
+}
+
+static void
+sockinfo(const struct sockaddr *sa, struct host_service *hs)
+{
+	static const int flags = NI_NUMERICHOST | NI_NUMERICSERV;
+	int rv;
+
+	rv = getnameinfo(sa, sa->sa_len, hs->hs_host, sizeof hs->hs_host,
+	    hs->hs_service, sizeof hs->hs_service, flags);
+	if (rv == -1)
+		err(1, "getnameinfo");
+}
+
+static bool
+tcpdrop(const struct sockaddr *lsa, const struct sockaddr *fsa)
+{
+	struct host_service local, foreign;
+	struct sockaddr_storage addrs[2];
+	int rv;
+
+	memcpy(&addrs[TCPDROP_FOREIGN], fsa, fsa->sa_len);
+	memcpy(&addrs[TCPDROP_LOCAL], lsa, lsa->sa_len);
+
+	sockinfo(lsa, &local);
+	sockinfo(fsa, &foreign);
+
+	if (tcpdrop_list_commands) {
+		printf("tcpdrop %s %s %s %s\n", local.hs_host, local.hs_service,
+		    foreign.hs_host, foreign.hs_service);
+		return (true);
+	}
+
+	rv = sysctlbyname("net.inet.tcp.drop", NULL, NULL, &addrs,
+	    sizeof addrs);
+	if (rv == -1) {
+		warn("%s %s %s %s", local.hs_host, local.hs_service,
+		    foreign.hs_host, foreign.hs_service);
+		return (false);
+	}
+	printf("%s %s %s %s: dropped\n", local.hs_host, local.hs_service,
+	    foreign.hs_host, foreign.hs_service);
+	return (true);
+}
+
+static bool
+tcpdropall(void)
+{
+	struct xinpgen *head, *xinp;
+	struct xtcpcb *xpcb;
+	struct tcpcb *tp;
+	struct inpcb *inp;
+	bool ok;
+
+	ok = true;
+
+	head = getxpcblist("net.inet.tcp.pcblist");
+
+#define	XINP_NEXT(xinp)							\
+	((struct xinpgen *)((uintptr_t)(xinp) + (xinp)->xig_len))
+
+	for (xinp = XINP_NEXT(head); xinp->xig_len > sizeof *xinp;
+	    xinp = XINP_NEXT(xinp)) {
+		xpcb = (struct xtcpcb *)xinp;
+		tp = &xpcb->xt_tp;
+		inp = &xpcb->xt_inp;
+
+		/*
+		 * XXX
+		 * Check protocol, support just v4 or v6, etc.
+		 */
+
+		/* Ignore PCBs which were freed during copyout.  */
+		if (inp->inp_gencnt > head->xig_gen)
+			continue;
+
+		/* Skip listening sockets.  */
+		if (tp->t_state == TCPS_LISTEN)
+			continue;
+
+		if (!tcpdropconn(&inp->inp_inc))
+			ok = false;
 	}
-	memset(&hints, 0, sizeof(hints));
-	hints.ai_family = AF_UNSPEC;
-	hints.ai_socktype = SOCK_STREAM;
-	if ((gaierr = getaddrinfo(argv[1], argv[2], &hints, &laddr)) != 0)
-		errx(1, "%s port %s: %s", argv[1], argv[2],
-		    gai_strerror(gaierr));
-	if ((gaierr = getaddrinfo(argv[3], argv[4], &hints, &faddr)) != 0) {
-		freeaddrinfo(laddr);
-		errx(1, "%s port %s: %s", argv[3], argv[4],
-		    gai_strerror(gaierr));
+	free(head);
+
+	return (ok);
+}
+
+static bool
+tcpdropbyname(const char *lhost, const char *lport, const char *fhost,
+    const char *fport)
+{
+	static const struct addrinfo hints = {
+		/*
+		 * Look for streams in all domains.
+		 */
+		.ai_family = AF_UNSPEC,
+		.ai_socktype = SOCK_STREAM,
+	};
+	struct addrinfo *ail, *local, *aif, *foreign;
+	int error;
+	bool ok, infamily;
+
+	error = getaddrinfo(lhost, lport, &hints, &local);
+	if (error != 0)
+		errx(1, "getaddrinfo: %s port %s: %s", lhost, lport,
+		    gai_strerror(error));
+
+	error = getaddrinfo(fhost, fport, &hints, &foreign);
+	if (error != 0) {
+		freeaddrinfo(local); /* XXX gratuitous */
+		errx(1, "getaddrinfo: %s port %s: %s", lhost, lport,
+		    gai_strerror(error));
 	}
-	for (ail = laddr; ail; ail = ail->ai_next) {
-		for (aif = faddr; aif; aif = aif->ai_next) {
+
+	ok = true;
+	infamily = false;
+
+	/*
+	 * Try every combination of local and foreign address pairs.
+	 */
+	for (ail = local; ail != NULL; ail = ail->ai_next) {
+		for (aif = foreign; aif != NULL; aif = aif->ai_next) {
 			if (ail->ai_family != aif->ai_family)
 				continue;
-			memcpy(&addrs[0], aif->ai_addr, aif->ai_addrlen);
-			memcpy(&addrs[1], ail->ai_addr, ail->ai_addrlen);
-			if (getnameinfo(aif->ai_addr, aif->ai_addrlen,
-			    fhbuf, sizeof(fhbuf),
-			    fsbuf, sizeof(fsbuf),
-			    NI_NUMERICHOST | NI_NUMERICSERV) == -1)
-				err(1, "getnameinfo");
-			if (getnameinfo(ail->ai_addr, ail->ai_addrlen,
-			    lhbuf, sizeof(lhbuf),
-			    lsbuf, sizeof(lsbuf),
-			    NI_NUMERICHOST | NI_NUMERICSERV) == -1)
-				err(1, "getnameinfo");
-			if (sysctl(mib, sizeof (mib) / sizeof (int), NULL,
-			    NULL, &addrs, sizeof(addrs)) == -1) {
-				rval = 1;
-				warn("%s %s %s %s", lhbuf, lsbuf, fhbuf, fsbuf);
-			} else
-				printf("%s %s %s %s: dropped\n",
-				    lhbuf, lsbuf, fhbuf, fsbuf);
+			infamily = true;
+			if (!tcpdrop(ail->ai_addr, aif->ai_addr))
+				ok = false;
 		}
 	}
-	freeaddrinfo(laddr);
-	freeaddrinfo(faddr);
-	exit(rval);
+
+	if (!infamily) {
+		warnx("%s %s %s %s: different address families", lhost, lport,
+		    fhost, fport);
+		ok = false;
+	}
+
+	freeaddrinfo(local);
+	freeaddrinfo(foreign);
+
+	return (ok);
+}
+
+static bool
+tcpdropconn(const struct in_conninfo *inc)
+{
+	struct sockaddr *local, *foreign;
+	struct sockaddr_in6 sin6[2];
+	struct sockaddr_in sin4[2];
+
+	if ((inc->inc_flags & INC_ISIPV6) != 0) {
+		memset(sin6, 0, sizeof sin6);
+
+		sin6[TCPDROP_LOCAL].sin6_len = sizeof sin6[TCPDROP_LOCAL];
+		sin6[TCPDROP_LOCAL].sin6_family = AF_INET6;
+		sin6[TCPDROP_LOCAL].sin6_port = inc->inc_lport;
+		memcpy(&sin6[TCPDROP_LOCAL].sin6_addr, &inc->inc6_laddr,
+		    sizeof inc->inc6_laddr);
+		local = (struct sockaddr *)&sin6[TCPDROP_LOCAL];
+
+		sin6[TCPDROP_FOREIGN].sin6_len = sizeof sin6[TCPDROP_FOREIGN];
+		sin6[TCPDROP_FOREIGN].sin6_family = AF_INET6;
+		sin6[TCPDROP_FOREIGN].sin6_port = inc->inc_fport;
+		memcpy(&sin6[TCPDROP_FOREIGN].sin6_addr, &inc->inc6_faddr,
+		    sizeof inc->inc6_faddr);
+		foreign = (struct sockaddr *)&sin6[TCPDROP_FOREIGN];
+	} else {
+		memset(&sin4[TCPDROP_LOCAL], 0, sizeof sin4[TCPDROP_LOCAL]);
+
+		sin4[TCPDROP_LOCAL].sin_len = sizeof sin4[TCPDROP_LOCAL];
+		sin4[TCPDROP_LOCAL].sin_family = AF_INET;
+		sin4[TCPDROP_LOCAL].sin_port = inc->inc_lport;
+		memcpy(&sin4[TCPDROP_LOCAL].sin_addr, &inc->inc_laddr,
+		    sizeof inc->inc_laddr);
+		local = (struct sockaddr *)&sin4[TCPDROP_LOCAL];
+
+		sin4[TCPDROP_FOREIGN].sin_len = sizeof sin4[TCPDROP_FOREIGN];
+		sin4[TCPDROP_FOREIGN].sin_family = AF_INET;
+		sin4[TCPDROP_FOREIGN].sin_port = inc->inc_fport;
+		memcpy(&sin4[TCPDROP_FOREIGN].sin_addr, &inc->inc_faddr,
+		    sizeof inc->inc_faddr);
+		foreign = (struct sockaddr *)&sin4[TCPDROP_FOREIGN];
+	}
+
+	return (tcpdrop(local, foreign));
+}
+
+static void
+usage(void)
+{
+	fprintf(stderr,
+"usage: tcpdrop local-address local-port foreign-address foreign-port\n"
+"       tcpdrop [-l] -a\n");
+	exit(1);
 }