[PATCH 3/6] dhcp: Add option type table and value parser

[Anshu Kumari <anskuma@redhat.com>]

Add an RFC 2132 type lookup table mapping DHCP option codes to their
expected value formats, and a dhcp_opt_parse() function that converts
CLI string values into their binary wire representation.

Wire dhcp_opt_parse() into the --dhcp-opt handler so that values are
validated and encoded at configuration time.

Link: https://bugs.passt.top/show_bug.cgi?id=192
Signed-off-by: Anshu Kumari <anskuma@redhat.com>
---
 conf.c |   9 +++
 dhcp.c | 227 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 dhcp.h |  15 ++++
 3 files changed, 251 insertions(+)

diff --git a/conf.c b/conf.c
index 61a393f..3ec10ac 100644
--- a/conf.c
+++ b/conf.c
@@ -1485,6 +1485,7 @@ void conf(struct ctx *c, int argc, char **argv)
 			unsigned long code;
 			const char *comma;
 			char *end;
+			int len;
 
 			comma = strchr(optarg, ',');
 			if (!comma)
@@ -1499,7 +1500,15 @@ void conf(struct ctx *c, int argc, char **argv)
 				die("Too many --dhcp-opt entries (max %d)",
 				    MAX_CUSTOM_DHCP_OPTS);
 
+			len = dhcp_opt_parse(code, comma + 1,
+					     c->custom_opts[c->custom_opts_count].val,
+					     sizeof(c->custom_opts[0].val));
+			if (len < 0)
+				die("Invalid value for DHCP option %lu: %s",
+				    code, comma + 1);
+
 			c->custom_opts[c->custom_opts_count].code = code;
+			c->custom_opts[c->custom_opts_count].len = len;
 			if (snprintf_check(c->custom_opts[c->custom_opts_count].str,
 					   sizeof(c->custom_opts[0].str),
 					   "%s", comma + 1))
diff --git a/dhcp.c b/dhcp.c
index 1ff8cba..9220516 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -33,6 +33,233 @@
 #include "log.h"
 #include "dhcp.h"
 
+/**
+ * struct dhcp_opt_type_entry - Maps option code to RFC 2132 value type
+ * @code:	DHCP option code
+ * @type:	Expected value format
+ */
+static const struct dhcp_opt_type_entry {
+	uint8_t code;
+	enum dhcp_opt_type type;
+} dhcp_opt_types[] = {
+	{  1, DHCP_OPT_IPV4 },		/* Subnet Mask */
+	{  2, DHCP_OPT_UINT32 },	/* Time Offset */
+	{  3, DHCP_OPT_IPV4_LIST },	/* Router */
+	{  4, DHCP_OPT_IPV4_LIST },	/* Time Server */
+	{  5, DHCP_OPT_IPV4_LIST },	/* Name Server */
+
+	{  6, DHCP_OPT_IPV4_LIST },	/* Domain Name Server */
+	{  7, DHCP_OPT_IPV4_LIST },	/* Log Server */
+	{  8, DHCP_OPT_IPV4_LIST },	/* Cookie Server */
+	{  9, DHCP_OPT_IPV4_LIST },	/* LPR Server */
+	{ 10, DHCP_OPT_IPV4_LIST },	/* Impress Server */
+
+	{ 11, DHCP_OPT_IPV4_LIST },	/* Resource Location Server */
+	{ 12, DHCP_OPT_STR },		/* Host Name */
+	{ 13, DHCP_OPT_UINT16 },	/* Boot File Size */
+	{ 15, DHCP_OPT_STR },		/* Domain Name */
+	{ 16, DHCP_OPT_IPV4 },		/* Swap Server */
+
+	{ 17, DHCP_OPT_STR },		/* Root Path */
+	{ 19, DHCP_OPT_UINT8 },	/* IP Forwarding */
+	{ 23, DHCP_OPT_UINT8 },	/* Default IP TTL */
+	{ 26, DHCP_OPT_UINT16 },	/* Interface MTU */
+	{ 28, DHCP_OPT_IPV4 },		/* Broadcast Address */
+
+	{ 33, DHCP_OPT_IPV4_LIST },	/* Static Routes (dest+router pairs) */
+	{ 37, DHCP_OPT_UINT8 },	/* TCP Default TTL */
+	{ 38, DHCP_OPT_UINT32 },	/* TCP Keepalive Interval */
+	{ 40, DHCP_OPT_STR },		/* NIS Domain Name */
+	{ 41, DHCP_OPT_IPV4_LIST },	/* NIS Servers */
+
+	{ 42, DHCP_OPT_IPV4_LIST },	/* NTP Servers */
+	{ 44, DHCP_OPT_IPV4_LIST },	/* NetBIOS Name Server */
+	{ 50, DHCP_OPT_IPV4 },		/* Requested IP Address */
+	{ 51, DHCP_OPT_UINT32 },	/* IP Address Lease Time */
+	{ 53, DHCP_OPT_UINT8 },	/* DHCP Message Type */
+
+	{ 54, DHCP_OPT_IPV4 },		/* Server Identifier */
+	{ 57, DHCP_OPT_UINT16 },	/* Max DHCP Message Size */
+	{ 58, DHCP_OPT_UINT32 },	/* Renewal (T1) Time */
+	{ 59, DHCP_OPT_UINT32 },	/* Rebinding (T2) Time */
+	{ 60, DHCP_OPT_STR },		/* Vendor Class Identifier */
+
+	{ 61, DHCP_OPT_STR },		/* Client Identifier */
+	{ 66, DHCP_OPT_STR },		/* TFTP Server Name */
+	{ 67, DHCP_OPT_STR },		/* Bootfile Name */
+	{ 119, DHCP_OPT_STR },		/* Domain Search List (RFC 3397) */
+	{ 121, DHCP_OPT_ROUTES },	/* Classless Static Routes */
+
+	{ 252, DHCP_OPT_STR },		/* WPAD URL */
+};
+
+/**
+ * dhcp_opt_type_lookup() - Look up the value type for a DHCP option code
+ * @code:	DHCP option code
+ *
+ * Return: type from table
+ */
+static enum dhcp_opt_type dhcp_opt_type_lookup(uint8_t code)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(dhcp_opt_types); i++) {
+		if (dhcp_opt_types[i].code == code)
+			return dhcp_opt_types[i].type;
+	}
+
+	return DHCP_OPT_NONE;
+}
+
+/**
+ * dhcp_opt_parse() - Parse a DHCP option value
+ * @code:	DHCP option code (determines value type via lookup table)
+ * @str:	Value string from command line
+ * @buf:	Output buffer for binary value
+ * @buf_len:	Size of output buffer
+ *
+ * Return: number of bytes written to @buf, or -1 on error
+ */
+int dhcp_opt_parse(uint8_t code, const char *str, uint8_t *buf, size_t buf_len)
+{
+	enum dhcp_opt_type type = dhcp_opt_type_lookup(code);
+
+	switch (type) {
+	case DHCP_OPT_NONE: {
+		die("Unsupported DHCP option: %u,"
+		    " see passt(1) for supported codes",
+		    code);
+	}
+	case DHCP_OPT_IPV4: {
+		struct in_addr addr;
+
+		if (inet_pton(AF_INET, str, &addr) != 1)
+			return -1;
+		if (buf_len < sizeof(addr))
+			return -1;
+		memcpy(buf, &addr, sizeof(addr));
+		return sizeof(addr);
+	}
+	case DHCP_OPT_IPV4_LIST: {
+		char *tok, *saveptr;
+		char tmp[1024];
+		int len = 0;
+
+		if (snprintf_check(tmp, sizeof(tmp), "%s", str))
+			return -1;
+
+		for (tok = strtok_r(tmp, " ", &saveptr); tok;
+		     tok = strtok_r(NULL, " ", &saveptr)) {
+			struct in_addr addr;
+
+			if (inet_pton(AF_INET, tok, &addr) != 1)
+				return -1;
+			if (len + (int)sizeof(addr) > (int)buf_len)
+				return -1;
+			memcpy(buf + len, &addr, sizeof(addr));
+			len += sizeof(addr);
+		}
+		return len;
+	}
+	case DHCP_OPT_UINT8: {
+		unsigned long val;
+		char *end;
+
+		val = strtoul(str, &end, 0);
+		if (*end || val > 255 || buf_len < 1)
+			return -1;
+		buf[0] = val;
+		return 1;
+	}
+	case DHCP_OPT_UINT16: {
+		unsigned long val;
+		char *end;
+
+		val = strtoul(str, &end, 0);
+		if (*end || val > 65535 || buf_len < 2)
+			return -1;
+		buf[0] = (val >> 8) & 0xff;
+		buf[1] = val & 0xff;
+		return 2;
+	}
+	case DHCP_OPT_UINT32: {
+		unsigned long val;
+		char *end;
+
+		val = strtoul(str, &end, 0);
+		if (*end || buf_len < 4)
+			return -1;
+		buf[0] = (val >> 24) & 0xff;
+		buf[1] = (val >> 16) & 0xff;
+		buf[2] = (val >>  8) & 0xff;
+		buf[3] = val & 0xff;
+		return 4;
+	}
+	case DHCP_OPT_ROUTES: {
+		/* RFC 3442: "CIDR/mask,gateway" entries, space-separated
+		 * Encodes as: mask-width + significant-octets + router
+		 * e.g. "192.168.1.0/24,10.0.0.1 0.0.0.0/0,10.0.0.1"
+		 */
+		char *tok, *saveptr;
+		char tmp[1024];
+		int len = 0;
+
+		if (snprintf_check(tmp, sizeof(tmp), "%s", str))
+			return -1;
+
+		for (tok = strtok_r(tmp, " ", &saveptr); tok;
+		     tok = strtok_r(NULL, " ", &saveptr)) {
+			struct in_addr dest, gw;
+			char *slash, *comma;
+			unsigned long mask;
+			int sig_octets;
+
+			slash = strchr(tok, '/');
+			if (!slash)
+				return -1;
+			*slash = '\0';
+
+			if (inet_pton(AF_INET, tok, &dest) != 1)
+				return -1;
+
+			comma = strchr(slash + 1, ',');
+			if (!comma)
+				return -1;
+			*comma = '\0';
+
+			mask = strtoul(slash + 1, NULL, 10);
+			if (mask > 32)
+				return -1;
+
+			if (inet_pton(AF_INET, comma + 1, &gw) != 1)
+				return -1;
+
+			sig_octets = (mask + 7) / 8;
+
+			if (len + 1 + sig_octets + 4 > (int)buf_len)
+				return -1;
+
+			buf[len++] = mask;
+			memcpy(buf + len, &dest, sig_octets);
+			len += sig_octets;
+			memcpy(buf + len, &gw, 4);
+			len += 4;
+		}
+		return len;
+	}
+	case DHCP_OPT_STR: {
+		size_t len = strlen(str);
+
+		if (!len || len >= buf_len)
+			return -1;
+		strncpy((char *)buf, str, buf_len);
+		return len;
+	}
+	}
+
+	return -1;
+}
+
 /**
  * struct opt - DHCP option
  * @sent:	Convenience flag, set while filling replies
diff --git a/dhcp.h b/dhcp.h
index cd50c99..01b2290 100644
--- a/dhcp.h
+++ b/dhcp.h
@@ -6,7 +6,22 @@
 #ifndef DHCP_H
 #define DHCP_H
 
+/**
+ * enum dhcp_opt_type - DHCP option value types per RFC 2132
+ */
+enum dhcp_opt_type {
+	DHCP_OPT_NONE,
+	DHCP_OPT_STR,
+	DHCP_OPT_IPV4,
+	DHCP_OPT_IPV4_LIST,
+	DHCP_OPT_UINT8,
+	DHCP_OPT_UINT16,
+	DHCP_OPT_UINT32,
+	DHCP_OPT_ROUTES,
+};
+
 int dhcp(const struct ctx *c, struct iov_tail *data);
 void dhcp_init(void);
+int dhcp_opt_parse(uint8_t code, const char *str, uint8_t *buf, size_t buf_len);
 
 #endif /* DHCP_H */
-- 
2.54.0