[PATCH 1/3] fwd_rule: Parse target adddresses 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 | 38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/fwd_rule.c b/fwd_rule.c
index ca409eaf..e8abc884 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 traget 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 = {
@@ -395,9 +398,17 @@ static void fwd_rule_range_except(struct fwd_table *fwd, bool del,
 		.flags = flags,
 	};
 	char rulestr[FWD_RULE_STRLEN];
-	unsigned delta = to - first;
+	unsigned delta = tgt_first - first;
 	unsigned base, i;
 
+	if (tgt_addr && !inany_is_unspecified(tgt_addr)) {
+		char astr[INANY_ADDRSTRLEN];
+
+		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) {
@@ -458,14 +469,17 @@ 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)
  * @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;
 
@@ -481,6 +495,12 @@ static bool parse_port_chunk(const char **cursor,
 		kind = CHUNK_INCLUDE;
 
 		if (parse_literal(&p, ":")) {
+			const char *tgtspec = p;
+
+			if (!parse_inany(&p, &taddr_tmp)	||
+			    !parse_literal(&p, "/"))
+				p = tgtspec; /* No target address, backtrack */
+
 			if (!parse_port_range(&p, &tr))
 				return false;
 		} else {
@@ -492,6 +512,8 @@ static bool parse_port_chunk(const char **cursor,
 
 	*kindp = kind;
 	*lrange = lr;
+	if (taddr)
+		*taddr = taddr_tmp;
 	if (trange)
 		*trange = tr;
 	*cursor = p;
@@ -561,7 +583,7 @@ 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) {
@@ -586,8 +608,9 @@ 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) {
@@ -604,7 +627,8 @@ 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 +644,7 @@ 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);
+				      NULL, 1, flags | FWD_WEAK);
 	}
 	return;
 bad:
-- 
2.54.0