[PATCH v2 1/2] fwd_rule: Parse target addresses for forwarding rules

[David Gibson <david@gibson.dropbear.id.au>]

Extend the parsing of forwarding rules (-[tu]) to allow the destination
address on the target side to be specified.  For now just parse them, and
give an error if we try to create rules with a specified target address.
We'll implement the actual forwarding logic in another patch.

Format (for either command line or pesto):
      -t 2222:192.0.2.1/2222

This should work along with all the other bits, that is, say:
      -t 192.0.2.1%eth0/2222-2225:192.0.2.2/22-25

FIXME: Ban for -[TU] for now
FIXME: Check interaction with splice handling

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
[dwg: Syntax from Stefano's earlier draft, largely rewritten on top of new
 parsing helpers]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 fwd_rule.c | 90 +++++++++++++++++++++++++++++++++++++++++++++---------
 passt.1    | 31 +++++++++++++------
 2 files changed, 98 insertions(+), 23 deletions(-)

diff --git a/fwd_rule.c b/fwd_rule.c
index ef35e1b4..bed29ed9 100644
--- a/fwd_rule.c
+++ b/fwd_rule.c
@@ -378,14 +378,17 @@ int fwd_rule_add(struct fwd_table *fwd, const struct fwd_rule *new)
  * @first:	First port to forward
  * @last:	Last port to forward
  * @exclude:	Bitmap of ports to exclude (may be NULL)
- * @to:		Port to translate @first to when forwarding
+ * @tgt_addr:	Destination address on the target side
+ * @tgt_first:	Destination port to use for @first on the target side
  * @flags:	Flags for forwarding entries
  */
 static void fwd_rule_range_except(struct fwd_table *fwd, bool del,
 				  uint8_t proto, const union inany_addr *addr,
 				  const char *ifname,
 				  uint16_t first, uint16_t last,
-				  const uint8_t *exclude, uint16_t to,
+				  const uint8_t *exclude,
+				  const union inany_addr *tgt_addr,
+				  uint16_t tgt_first,
 				  uint8_t flags)
 {
 	struct fwd_rule rule = {
@@ -394,10 +397,31 @@ static void fwd_rule_range_except(struct fwd_table *fwd, bool del,
 		.proto = proto,
 		.flags = flags,
 	};
+	unsigned delta = tgt_first - first;
 	char rulestr[FWD_RULE_STRLEN];
-	unsigned delta = to - first;
 	unsigned base, i;
 
+	if (tgt_addr && !inany_is_unspecified(tgt_addr)) {
+		char astr[INANY_ADDRSTRLEN];
+
+		if (!inany_is_unicast(tgt_addr)) {
+			die("Target address %s is not unicast",
+			    inany_ntop(tgt_addr, astr, sizeof(astr)));
+		}
+		if (!addr || !!inany_v4(addr) != !!inany_v4(tgt_addr)) {
+			char bstr[INANY_ADDRSTRLEN];
+
+			die(
+"Forwarding between IP versions (%s => %s) not implemented",
+			    inany_ntop(addr, bstr, sizeof(bstr)),
+			    inany_ntop(tgt_addr, astr, sizeof(astr)));
+		}
+
+		info("Target address: %s",
+		     inany_ntop(tgt_addr, astr, sizeof(astr)));
+		die("Target address remapping not yet implemented");
+	}
+
 	if (!addr)
 		rule.flags |= FWD_DUAL_STACK_ANY;
 	if (ifname) {
@@ -458,19 +482,31 @@ enum fwd_port_chunk_kind {
  * @cursor:	Parsing point (see parse.c)
  * @kindp:	Updated with kind of chunk we parsed
  * @lrange:	Updated with listening port range (for INCLUDE & EXCLUDE)
+ * @taddr:	Updated with target address (for INCLUDE & ALL)
  * @trange:	Updated with target port range (for INCLUDE)
  */
 static bool parse_port_chunk(const char **cursor,
 			     enum fwd_port_chunk_kind *kindp,
 			     struct port_range *lrange,
+			     union inany_addr *taddr,
 			     struct port_range *trange)
 {
 	struct port_range lr = { 0 }, tr = { 0 };
+	union inany_addr taddr_tmp = inany_any6;
 	enum fwd_port_chunk_kind kind;
 	const char *p = *cursor;
 
 	if (parse_literal(&p, "all")) {
+		const char *tgtspec = p;
+
 		kind = CHUNK_ALL;
+		if (p = tgtspec,
+		    parse_literal(&p, ":")		&&
+		    parse_inany(&p, &taddr_tmp)) {
+			/* Target address */
+		} else {
+			p = tgtspec;
+		}
 	} else if (parse_literal(&p, "auto")) {
 		kind = CHUNK_AUTO;
 	} else if (parse_literal(&p, "~")) {
@@ -478,12 +514,29 @@ static bool parse_port_chunk(const char **cursor,
 		if (!parse_port_range(&p, &lr))
 			return false;
 	} else if (parse_port_range(&p, &lr)) {
-		kind = CHUNK_INCLUDE;
+		const char *tgtspec = p;
 
-		if (parse_literal(&p, ":")) {
-			if (!parse_port_range(&p, &tr))
-				return false;
+		kind = CHUNK_INCLUDE;
+		if (p = tgtspec,
+		    parse_literal(&p, ":")		&&
+		    parse_inany(&p, &taddr_tmp)		&&
+		    parse_literal(&p, "/")		&&
+		    parse_port_range(&p, &tr)) {
+			/* Target address & range */
+		} else if (p = tgtspec,
+			   parse_literal(&p, ":")	&&
+			   parse_inany(&p, &taddr_tmp)) {
+			/* Target address only */
+			tr = lr;
+		} else if (p = tgtspec,
+			   parse_literal(&p, ":")	&&
+			   parse_port_range(&p, &tr)) {
+			/* Target range only */
+			taddr_tmp = inany_any6;
 		} else {
+			p = tgtspec;
+			/* No target specification */
+			taddr_tmp = inany_any6;
 			tr = lr;
 		}
 	} else {
@@ -492,6 +545,8 @@ static bool parse_port_chunk(const char **cursor,
 
 	*kindp = kind;
 	*lrange = lr;
+	if (taddr)
+		*taddr = taddr_tmp;
 	if (trange)
 		*trange = tr;
 	*cursor = p;
@@ -551,6 +606,7 @@ static void fwd_rule_parse_ports(struct fwd_table *fwd, bool del, uint8_t proto,
 				 const char *spec)
 {
 	uint8_t exclude[PORT_BITMAP_SIZE] = { 0 };
+	union inany_addr all_taddr = inany_any6;
 	enum fwd_port_chunk_kind kind;
 	struct port_range lrange;
 	bool exclude_only = true;
@@ -561,7 +617,7 @@ static void fwd_rule_parse_ports(struct fwd_table *fwd, bool del, uint8_t proto,
 	/* Consider excluded ranges and "auto" in the first pass */
 	p = spec;
 	do {
-		if (!parse_port_chunk(&p, &kind, &lrange, NULL))
+		if (!parse_port_chunk(&p, &kind, &lrange, NULL, NULL))
 			goto bad;
 
 		switch (kind) {
@@ -586,14 +642,19 @@ static void fwd_rule_parse_ports(struct fwd_table *fwd, bool del, uint8_t proto,
 	p = spec;
 	do {
 		struct port_range trange;
+		union inany_addr taddr;
 
-		if (!parse_port_chunk(&p, &kind, &lrange, &trange))
+		if (!parse_port_chunk(&p, &kind, &lrange, &taddr, &trange))
 			goto bad;
 
 		switch (kind) {
-		case CHUNK_AUTO:	/* already handled */
-		case CHUNK_EXCLUDE:	/* already handled */
-		case CHUNK_ALL:		/* handled later */
+		case CHUNK_AUTO:
+		case CHUNK_EXCLUDE:
+			continue; /* already handled */
+
+		case CHUNK_ALL:
+			/* Save the address to use later */
+			all_taddr = taddr;
 			continue;
 
 		case CHUNK_INCLUDE:
@@ -604,7 +665,8 @@ static void fwd_rule_parse_ports(struct fwd_table *fwd, bool del, uint8_t proto,
 
 			fwd_rule_range_except(fwd, del, proto, addr, ifname,
 					      lrange.first, lrange.last,
-					      exclude, trange.first, flags);
+					      exclude, &taddr, trange.first,
+					      flags);
 			break;
 		default:
 			goto bad;
@@ -620,7 +682,7 @@ static void fwd_rule_parse_ports(struct fwd_table *fwd, bool del, uint8_t proto,
 
 		fwd_rule_range_except(fwd, del, proto, addr, ifname,
 				      1, NUM_PORTS - 1, exclude,
-				      1, flags | FWD_WEAK);
+				      &all_taddr, 1, flags | FWD_WEAK);
 	}
 	return;
 bad:
diff --git a/passt.1 b/passt.1
index c3722ef9..9ece0e0c 100644
--- a/passt.1
+++ b/passt.1
@@ -449,12 +449,15 @@ interface name (since Linux 5.7) can be specified.
 
 \fIports\fR is a comma-separated list of entries which may be any of:
 .TP
-\fIfirst\fR[\fB-\fR\fIlast\fR][\fB:\fR\fItofirst\fR[\fB-\fR\fItolast\fR]]
+\fIfirst\fR[\fB-\fR\fIlast\fR][\fB:\fR[\fItoaddr\fR\fB/\fR]\fItofirst\fR[\fB-\fR\fItolast\fR]]
+.TP
+\fIfirst\fR[\fB-\fR\fIlast\fR][\fB:\fR\fItoaddr\fR]
 Include range. Forward port numbers between \fIfirst\fR and \fIlast\fR
-(inclusive) to ports between \fItofirst\fR and \fItolast\fR.  If
-\fItofirst\fR and \fItolast\fR are omitted, assume the same as
-\fIfirst\fR and \fIlast\fR.  If \fIlast\fR is omitted, assume the same
-as \fIfirst\fR.
+(inclusive) to ports between \fItofirst\fR and \fItolast\fR to address
+\fItoaddr\fR.  If \fItoaddr\fR is omitted, automatically determine the
+guest or namespace address.  If \fItofirst\fR and \fItolast\fR are
+omitted, assume the same as \fIfirst\fR and \fIlast\fR.  If \fIlast\fR
+is omitted, assume the same as \fIfirst\fR.
 
 .TP
 \fB~\fR\fIfirst\fR[\fB-\fR\fIlast\fR]
@@ -462,11 +465,13 @@ Exclude range.  Don't forward port numbers between \fIfirst\fR and
 \fIlast\fR.  This takes precedences over include ranges.
 
 .TP
-.BR all
+.BR all\fR[\fB:\fItoaddr\fR]
 Forward all unbound, non-ephemeral ports, not covered by exclude
-ranges above, as permitted by current capabilities.  For low (< 1024)
-ports, see \fBNOTES\fR. No failures are reported for unavailable
-ports, unless no ports could be forwarded at all.
+ranges above, as permitted by current capabilities, to the
+corresponding ports on address \fItoaddr\fR.  If \fItoaddr\fR is
+omitted, automatically determine the guest or namespace address.  For
+low (< 1024) ports, see \fBNOTES\fR. No failures are reported for
+unavailable ports, unless no ports could be forwarded at all.
 
 .TP
 .BR auto
@@ -516,6 +521,14 @@ Forward local port 22, bound to 192.0.2.1 and interface eth0, to port 22
 -t %eth0/22
 Forward local port 22, bound to any address on interface eth0, to port 22
 .TP
+-t 0.0.0.0/5000:192.0.2.5/6000
+Forward local port 5000, bound to any IPv4 address, to port 6000 on address 192.0.2.5.
+.TP
+-t 127.0.0.6/all:192.0.2.6
+For the local address 127.0.0.6 forward all unbound, non-ephemeral
+ports as permitted by current capabilities to the corresponding port
+on 192.0.2.6.
+.TP
 -t 2000-5000,~3000-3010
 Forward local ports between 2000 and 5000, except for those between 3000 and
 3010
-- 
2.55.0