Adapt OpenBSD pf's "sloopy" TCP state machine which is useful for Direct

Server Return mode, where not all packets would be visible to the load
balancer or gateway.

This commit should be reverted when we merge future pf versions.  The
benefit it would provide is that this version does not break any existing
public interface and thus won't be a problem if we want to MFC it to
earlier FreeBSD releases.

Discussed with:	mlaier
Obtained from:	OpenBSD
Sponsored by:	iXsystems, Inc.
MFC after:	1 month

4 files changed, 45 insertions, 4 deletions

diff --git a/contrib/pf/man/pf.conf.5 b/contrib/pf/man/pf.conf.5
index 67cb717..98c3d0e 100644
--- a/contrib/pf/man/pf.conf.5
+++ b/contrib/pf/man/pf.conf.5
@@ -28,7 +28,7 @@
 .\" ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd October 30, 2006
+.Dd June 10, 2008
 .Dt PF.CONF 5
 .Os
 .Sh NAME
@@ -2059,6 +2059,13 @@ Changes the timeout values used for states created by this rule.
 For a list of all valid timeout names, see
 .Sx OPTIONS
 above.
+.It Ar sloppy
+Uses a sloppy TCP connection tracker that does not check sequence
+numbers at all, which makes insertion and ICMP teardown attacks way
+easier.
+This is intended to be used in situations where one does not see all
+packets of a connection, i.e. in asymmetric routing situations.
+Cannot be used with modulate or synproxy state.
 .El
 .Pp
 Multiple options can be specified, separated by commas:
@@ -2923,7 +2930,7 @@ tos            = "tos" ( "lowdelay" | "throughput" | "reliability" |
                  [ "0x" ] number )
 
 state-opts     = state-opt [ [ "," ] state-opts ]
-state-opt      = ( "max" number | "no-sync" | timeout |
+state-opt      = ( "max" number | "no-sync" | timeout | sloppy |
                  "source-track" [ ( "rule" | "global" ) ] |
                  "max-src-nodes" number | "max-src-states" number |
                  "max-src-conn" number |
diff --git a/contrib/pf/pfctl/parse.y b/contrib/pf/pfctl/parse.y
index 9817e8e..c22a0b6 100644
--- a/contrib/pf/pfctl/parse.y
+++ b/contrib/pf/pfctl/parse.y
@@ -128,7 +128,7 @@ enum	{ PF_STATE_OPT_MAX, PF_STATE_OPT_NOSYNC, PF_STATE_OPT_SRCTRACK,
 	    PF_STATE_OPT_MAX_SRC_STATES, PF_STATE_OPT_MAX_SRC_CONN,
 	    PF_STATE_OPT_MAX_SRC_CONN_RATE, PF_STATE_OPT_MAX_SRC_NODES,
 	    PF_STATE_OPT_OVERLOAD, PF_STATE_OPT_STATELOCK,
-	    PF_STATE_OPT_TIMEOUT };
+	    PF_STATE_OPT_TIMEOUT, PF_STATE_OPT_SLOPPY };
 
 enum	{ PF_SRCTRACK_NONE, PF_SRCTRACK, PF_SRCTRACK_GLOBAL, PF_SRCTRACK_RULE };
 
@@ -423,7 +423,7 @@ typedef struct {
 %token	QUEUE PRIORITY QLIMIT RTABLE
 %token	LOAD RULESET_OPTIMIZATION
 %token	STICKYADDRESS MAXSRCSTATES MAXSRCNODES SOURCETRACK GLOBAL RULE
-%token	MAXSRCCONN MAXSRCCONNRATE OVERLOAD FLUSH
+%token	MAXSRCCONN MAXSRCCONNRATE OVERLOAD FLUSH SLOPPY
 %token	TAGGED TAG IFBOUND FLOATING STATEPOLICY ROUTE
 %token	<v.string>		STRING
 %token	<v.i>			PORTBINARY
@@ -1891,6 +1891,14 @@ pfrule		: action dir logquick interface route af proto fromto
 					statelock = 1;
 					r.rule_flag |= o->data.statelock;
 					break;
+				case PF_STATE_OPT_SLOPPY:
+					if (r.rule_flag & PFRULE_STATESLOPPY) {
+						yyerror("state sloppy option: "
+						    "multiple definitions");
+						YYERROR;
+					}
+					r.rule_flag |= PFRULE_STATESLOPPY;
+					break;
 				case PF_STATE_OPT_TIMEOUT:
 					if (o->data.timeout.number ==
 					    PFTM_ADAPTIVE_START ||
@@ -3216,6 +3224,14 @@ state_opt_item	: MAXIMUM number		{
 			$$->next = NULL;
 			$$->tail = $$;
 		}
+		| SLOPPY {
+			$$ = calloc(1, sizeof(struct node_state_opt));
+			if ($$ == NULL)
+				err(1, "state_opt_item: calloc");
+			$$->type = PF_STATE_OPT_SLOPPY;
+			$$->next = NULL;
+			$$->tail = $$;
+		}
 		| STRING number			{
 			int	i;
 
@@ -4101,6 +4117,13 @@ filter_consistent(struct pf_rule *r, int anchor_call)
 		yyerror("keep state on block rules doesn't make sense");
 		problems++;
 	}
+	if (r->rule_flag & PFRULE_STATESLOPPY &&
+	    (r->keep_state == PF_STATE_MODULATE ||
+	    r->keep_state == PF_STATE_SYNPROXY)) {
+		yyerror("sloppy state matching cannot be used with "
+		    "synproxy state or modulate state");
+		problems++;
+	}
 	return (-problems);
 }
 
@@ -4969,6 +4992,7 @@ lookup(char *s)
 		{ "scrub",		SCRUB},
 		{ "set",		SET},
 		{ "skip",		SKIP},
+		{ "sloppy",		SLOPPY},
 		{ "source-hash",	SOURCEHASH},
 		{ "source-track",	SOURCETRACK},
 		{ "state",		STATE},
diff --git a/contrib/pf/pfctl/pf_print_state.c b/contrib/pf/pfctl/pf_print_state.c
index b3a693a..02a39b3 100644
--- a/contrib/pf/pfctl/pf_print_state.c
+++ b/contrib/pf/pfctl/pf_print_state.c
@@ -294,6 +294,8 @@ print_state(struct pf_state *s, int opts)
 			printf(", anchor %u", s->anchor.nr);
 		if (s->rule.nr != -1)
 			printf(", rule %u", s->rule.nr);
+		if (s->state_flags & PFSTATE_SLOPPY)
+			printf(", sloppy");
 		if (s->src_node != NULL)
 			printf(", source-track");
 		if (s->nat_src_node != NULL)
diff --git a/contrib/pf/pfctl/pfctl_parser.c b/contrib/pf/pfctl/pfctl_parser.c
index 9f232bd..c9b2e11 100644
--- a/contrib/pf/pfctl/pfctl_parser.c
+++ b/contrib/pf/pfctl/pfctl_parser.c
@@ -873,6 +873,8 @@ print_rule(struct pf_rule *r, const char *anchor_call, int verbose)
 		opts = 1;
 	if (r->rule_flag & PFRULE_IFBOUND)
 		opts = 1;
+	if (r->rule_flag & PFRULE_STATESLOPPY)
+		opts = 1;
 	for (i = 0; !opts && i < PFTM_MAX; ++i)
 		if (r->timeout[i])
 			opts = 1;
@@ -939,6 +941,12 @@ print_rule(struct pf_rule *r, const char *anchor_call, int verbose)
 			printf("if-bound");
 			opts = 0;
 		}
+		if (r->rule_flag & PFRULE_STATESLOPPY) {
+			if (!opts)
+				printf(", ");
+			printf("sloppy");
+			opts = 0;
+		}
 		for (i = 0; i < PFTM_MAX; ++i)
 			if (r->timeout[i]) {
 				int j;