[PATCH v2 20/23] fwd, conf: Add capabilities bits to each forwarding table

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

conf_ports_spec() and conf_ports() take the global context structure, but
their only use for it is seeing if various things are possible: which
protocols and address formats are allowed in formatting rules.  Localise
that information into the forwarding table, with a capabilities bitmap.

For now we set that caps map to the same thing for all tables, but keep it
per-table to allow for the possibility of different pif types in future
that might have different capabilities (e.g. if we add a forwarding table
for the tap interface, it won't be able to accept interface names to bind).

Use this information to remove the global context parameter from
conf_ports() and conf_ports_spec().

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 conf.c     | 48 ++++++++++++++++++++++--------------------------
 fwd.c      | 17 +++++++++++++++++
 fwd.h      |  2 ++
 fwd_rule.h |  8 ++++++++
 4 files changed, 49 insertions(+), 26 deletions(-)

diff --git a/conf.c b/conf.c
index 89f68de7..b7a4459e 100644
--- a/conf.c
+++ b/conf.c
@@ -218,15 +218,13 @@ fail:
 
 /**
  * conf_ports_spec() - Parse port range(s) specifier
- * @c:		Execution context
  * @fwd:	Forwarding table to be updated
  * @proto:	Protocol to forward
  * @addr:	Listening address for forwarding
  * @ifname:	Interface name for listening
  * @spec:	Port range(s) specifier
  */
-static void conf_ports_spec(const struct ctx *c,
-			    struct fwd_table *fwd, uint8_t proto,
+static void conf_ports_spec(struct fwd_table *fwd, uint8_t proto,
 			    const union inany_addr *addr, const char *ifname,
 			    const char *spec)
 {
@@ -255,7 +253,7 @@ static void conf_ports_spec(const struct ctx *c,
 			if (p != ep) /* Garbage after the keyword */
 				goto bad;
 
-			if (c->mode != MODE_PASTA) {
+			if (!(fwd->caps & FWD_CAP_SCAN)) {
 				die(
 "'auto' port forwarding is only allowed for pasta");
 			}
@@ -329,13 +327,11 @@ bad:
 
 /**
  * conf_ports() - Parse port configuration options, initialise UDP/TCP sockets
- * @c:		Execution context
  * @optname:	Short option name, t, T, u, or U
  * @optarg:	Option argument (port specification)
  * @fwd:	Forwarding table to be updated
  */
-static void conf_ports(const struct ctx *c, char optname, const char *optarg,
-		       struct fwd_table *fwd)
+static void conf_ports(char optname, const char *optarg, struct fwd_table *fwd)
 {
 	union inany_addr addr_buf = inany_any6, *addr = &addr_buf;
 	char buf[BUFSIZ], *spec, *ifname = NULL;
@@ -360,9 +356,9 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg,
 		return;
 	}
 
-	if (proto == IPPROTO_TCP && c->no_tcp)
+	if (proto == IPPROTO_TCP && !(fwd->caps & FWD_CAP_TCP))
 		die("TCP port forwarding requested but TCP is disabled");
-	if (proto == IPPROTO_UDP && c->no_udp)
+	if (proto == IPPROTO_UDP && !(fwd->caps & FWD_CAP_UDP))
 		die("UDP port forwarding requested but UDP is disabled");
 
 	strncpy(buf, optarg, sizeof(buf) - 1);
@@ -410,10 +406,10 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg,
 	}
 
 	if (addr) {
-		if (!c->ifi4 && inany_v4(addr)) {
+		if (!(fwd->caps & FWD_CAP_IPV4) && inany_v4(addr)) {
 			die("IPv4 is disabled, can't use -%c %s",
 			    optname, optarg);
-		} else if (!c->ifi6 && !inany_v4(addr)) {
+		} else if (!(fwd->caps & FWD_CAP_IPV6) && !inany_v4(addr)) {
 			die("IPv6 is disabled, can't use -%c %s",
 			    optname, optarg);
 		}
@@ -422,17 +418,17 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg,
 	if (optname == 'T' || optname == 'U') {
 		assert(!addr && !ifname);
 
-		if (c->no_bindtodevice) {
+		if (!(fwd->caps & FWD_CAP_IFNAME)) {
 			warn(
 "SO_BINDTODEVICE unavailable, forwarding only 127.0.0.1 and ::1 for '-%c %s'",
 			     optname, optarg);
 
-			if (c->ifi4) {
-				conf_ports_spec(c, fwd, proto,
+			if (fwd->caps & FWD_CAP_IPV4) {
+				conf_ports_spec(fwd, proto,
 						&inany_loopback4, NULL, spec);
 			}
-			if (c->ifi6) {
-				conf_ports_spec(c, fwd, proto,
+			if (fwd->caps & FWD_CAP_IPV6) {
+				conf_ports_spec(fwd, proto,
 						&inany_loopback6, NULL, spec);
 			}
 			return;
@@ -441,13 +437,13 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg,
 		ifname = "lo";
 	}
 
-	if (ifname && c->no_bindtodevice) {
+	if (ifname && !(fwd->caps & FWD_CAP_IFNAME)) {
 		die(
 "Device binding for '-%c %s' unsupported (requires kernel 5.7+)",
 		    optname, optarg);
 	}
 
-	conf_ports_spec(c, fwd, proto, addr, ifname, spec);
+	conf_ports_spec(fwd, proto, addr, ifname, spec);
 }
 
 /**
@@ -2186,16 +2182,16 @@ void conf(struct ctx *c, int argc, char **argv)
 
 		if (name == 't') {
 			opt_t = true;
-			conf_ports(c, name, optarg, c->fwd[PIF_HOST]);
+			conf_ports(name, optarg, c->fwd[PIF_HOST]);
 		} else if (name == 'u') {
 			opt_u = true;
-			conf_ports(c, name, optarg, c->fwd[PIF_HOST]);
+			conf_ports(name, optarg, c->fwd[PIF_HOST]);
 		} else if (name == 'T') {
 			opt_T = true;
-			conf_ports(c, name, optarg, c->fwd[PIF_SPLICE]);
+			conf_ports(name, optarg, c->fwd[PIF_SPLICE]);
 		} else if (name == 'U') {
 			opt_U = true;
-			conf_ports(c, name, optarg, c->fwd[PIF_SPLICE]);
+			conf_ports(name, optarg, c->fwd[PIF_SPLICE]);
 		}
 	} while (name != -1);
 
@@ -2247,13 +2243,13 @@ void conf(struct ctx *c, int argc, char **argv)
 
 	if (c->mode == MODE_PASTA) {
 		if (!opt_t)
-			conf_ports(c, 't', "auto", c->fwd[PIF_HOST]);
+			conf_ports('t', "auto", c->fwd[PIF_HOST]);
 		if (!opt_T)
-			conf_ports(c, 'T', "auto", c->fwd[PIF_SPLICE]);
+			conf_ports('T', "auto", c->fwd[PIF_SPLICE]);
 		if (!opt_u)
-			conf_ports(c, 'u', "auto", c->fwd[PIF_HOST]);
+			conf_ports('u', "auto", c->fwd[PIF_HOST]);
 		if (!opt_U)
-			conf_ports(c, 'U', "auto", c->fwd[PIF_SPLICE]);
+			conf_ports('U', "auto", c->fwd[PIF_SPLICE]);
 	}
 
 	if (!c->quiet)
diff --git a/fwd.c b/fwd.c
index 3e87169b..c7fd1a9d 100644
--- a/fwd.c
+++ b/fwd.c
@@ -326,6 +326,23 @@ static struct fwd_table fwd_out;
  */
 void fwd_rule_init(struct ctx *c)
 {
+	uint32_t caps = 0;
+
+	if (c->ifi4)
+		caps |= FWD_CAP_IPV4;
+	if (c->ifi6)
+		caps |= FWD_CAP_IPV6;
+	if (!c->no_tcp)
+		caps |= FWD_CAP_TCP;
+	if (!c->no_udp)
+		caps |= FWD_CAP_UDP;
+	if (c->mode == MODE_PASTA)
+		caps |= FWD_CAP_SCAN;
+	if (!c->no_bindtodevice)
+		caps |= FWD_CAP_IFNAME;
+
+	fwd_in.caps = fwd_out.caps = caps;
+
 	c->fwd[PIF_HOST] = &fwd_in;
 	if (c->mode == MODE_PASTA)
 		c->fwd[PIF_SPLICE] = &fwd_out;
diff --git a/fwd.h b/fwd.h
index 43bfeadb..3e365d35 100644
--- a/fwd.h
+++ b/fwd.h
@@ -52,6 +52,7 @@ struct fwd_listen_ref {
 
 /**
  * struct fwd_table - Forwarding state (per initiating pif)
+ * @caps:	Forwarding capabilities for this initiating pif
  * @count:	Number of forwarding rules
  * @rules:	Array of forwarding rules
  * @rulesocks:	Parallel array of @rules (@count valid entries) of pointers to
@@ -61,6 +62,7 @@ struct fwd_listen_ref {
  * @socks:	Listening sockets for forwarding
  */
 struct fwd_table {
+	uint32_t caps;
 	unsigned count;
 	struct fwd_rule rules[MAX_FWD_RULES];
 	int *rulesocks[MAX_FWD_RULES];
diff --git a/fwd_rule.h b/fwd_rule.h
index 8506a0c4..edba6782 100644
--- a/fwd_rule.h
+++ b/fwd_rule.h
@@ -17,6 +17,14 @@
 #include "inany.h"
 #include "bitmap.h"
 
+/* Forwarding capability bits */
+#define FWD_CAP_IPV4		BIT(0)
+#define FWD_CAP_IPV6		BIT(1)
+#define FWD_CAP_TCP		BIT(2)
+#define FWD_CAP_UDP		BIT(3)
+#define FWD_CAP_SCAN		BIT(4)
+#define FWD_CAP_IFNAME		BIT(5)
+
 /**
  * struct fwd_rule - Forwarding rule governing a range of ports
  * @addr:	Address to forward from
-- 
2.53.0