[PATCH v2 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>
---
v2:
  - Replaced struct lookup table + dhcp_opt_type_lookup() function with flat dhcp_opt_types[256] array indexed by code.
  - Consolidated DHCP_OPT_UINT8/UINT16/UINT32 into single DHCP_OPT_INTEGER with dhcp_opt_int_width[256] table.
  - Dropped DHCP_OPT_ROUTES / option 121 entirely.
  - Added kerneldoc for enum dhcp_opt_type values.
  - Removed curly braces from switch cases, declarations before switch.
  - Added newlines before return statements.
  - Changed IP list delimiter from space to comma (--dhcp-opt 6,1.1.1.1,8.8.8.8).
  - Defined DHCP_OPT_PARSE_BUF constant for bare 1024.
  - Added len and val[255] fields to struct here (moved from patch 1).
  - Added kerneldoc for @custom_opts.len and @custom_opts.val.
  - Wired dhcp_opt_parse() into case 32 (--dhcp-boot) to populate val/len.
---
 conf.c  |  16 ++++++
 dhcp.c  | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 dhcp.h  |  17 +++++++
 passt.h |   4 ++
 4 files changed, 185 insertions(+)

diff --git a/conf.c b/conf.c
index ae8ee26..3a5f45d 100644
--- a/conf.c
+++ b/conf.c
@@ -1266,6 +1266,7 @@ void conf(struct ctx *c, int argc, char **argv)
 	char *end;
 	uid_t uid;
 	gid_t gid;
+	int len;
 	
 
 	if (c->mode == MODE_PASTA)
@@ -1482,7 +1483,14 @@ void conf(struct ctx *c, int argc, char **argv)
 				die("Too many DHCP options (max %d)",
 				    MAX_CUSTOM_DHCP_OPTS);
 
+			ret = dhcp_opt_parse(67, optarg,
+					     c->custom_opts[c->custom_opts_count].val,
+					     sizeof(c->custom_opts[0].val));
+			if (ret < 0)
+				die("Invalid boot file value: %s", optarg);
+
 			c->custom_opts[c->custom_opts_count].code = 67;
+			c->custom_opts[c->custom_opts_count].len = ret;
 			if (snprintf_check(c->custom_opts[c->custom_opts_count].str,
 					   sizeof(c->custom_opts[0].str),
 					   "%s", optarg))
@@ -1503,7 +1511,15 @@ 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(optcode, 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",
+				    optcode, comma + 1);
+
 			c->custom_opts[c->custom_opts_count].code = optcode;
+			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..e1c95ad 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -33,6 +33,154 @@
 #include "log.h"
 #include "dhcp.h"
 
+/**
+ * dhcp_opt_types - Maps option code to RFC 2132 value type, indexed by code
+ */
+static const enum dhcp_opt_type dhcp_opt_types[256] = {
+	[1]  = DHCP_OPT_IPV4,		/* Subnet Mask */
+	[2]  = DHCP_OPT_INTEGER,	/* 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_INTEGER,	/* Boot File Size */
+	[15] = DHCP_OPT_STR,		/* Domain Name */
+	[16] = DHCP_OPT_IPV4,		/* Swap Server */
+	[17] = DHCP_OPT_STR,		/* Root Path */
+	[19] = DHCP_OPT_INTEGER,	/* IP Forwarding */
+	[23] = DHCP_OPT_INTEGER,	/* Default IP TTL */
+	[26] = DHCP_OPT_INTEGER,	/* Interface MTU */
+	[28] = DHCP_OPT_IPV4,		/* Broadcast Address */
+	[33] = DHCP_OPT_IPV4_LIST,	/* Static Routes */
+	[37] = DHCP_OPT_INTEGER,	/* TCP Default TTL */
+	[38] = DHCP_OPT_INTEGER,	/* 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_INTEGER,	/* IP Address Lease Time */
+	[53] = DHCP_OPT_INTEGER,	/* DHCP Message Type */
+	[54] = DHCP_OPT_IPV4,		/* Server Identifier */
+	[55] = DHCP_OPT_STR,		/* Parameter Request List */
+	[57] = DHCP_OPT_INTEGER,	/* Max DHCP Message Size */
+	[58] = DHCP_OPT_INTEGER,	/* Renewal (T1) Time */
+	[59] = DHCP_OPT_INTEGER,	/* 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 */
+	[252] = DHCP_OPT_STR,		/* WPAD URL */
+};
+
+/**
+ * dhcp_opt_int_width - Integer width in bytes for INTEGER-typed options
+ */
+static const uint8_t dhcp_opt_int_width[256] = {
+	[2]  = 4,	/* Time Offset */
+	[13] = 2,	/* Boot File Size */
+	[19] = 1,	/* IP Forwarding */
+	[23] = 1,	/* Default IP TTL */
+	[26] = 2,	/* Interface MTU */
+	[37] = 1,	/* TCP Default TTL */
+	[38] = 4,	/* TCP Keepalive Interval */
+	[51] = 4,	/* IP Address Lease Time */
+	[53] = 1,	/* DHCP Message Type */
+	[57] = 2,	/* Max DHCP Message Size */
+	[58] = 4,	/* Renewal (T1) Time */
+	[59] = 4,	/* Rebinding (T2) Time */
+};
+
+#define DHCP_OPT_PARSE_BUF	1024
+
+/**
+ * dhcp_opt_parse() - Parse a DHCP option value
+ * @code:	DHCP option code
+ * @str:	DHCP Value string from command line
+ * @buf:	Output buffer
+ * @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_types[code];
+	char tmp[DHCP_OPT_PARSE_BUF];
+	char *tok, *saveptr, *end;
+	struct in_addr addr;
+	unsigned long val;
+	unsigned int i;
+	uint8_t width;
+	size_t slen;
+	int len;
+
+	switch (type) {
+	case DHCP_OPT_NONE:
+		die("Unsupported DHCP option: %u,"
+		    " see passt(1) for supported codes", code);
+	case DHCP_OPT_IPV4:
+		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:
+		len = 0;
+
+		if (snprintf_check(tmp, sizeof(tmp), "%s", str))
+			return -1;
+
+		for (tok = strtok_r(tmp, ",", &saveptr); tok;
+		     tok = strtok_r(NULL, ",", &saveptr)) {
+			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_INTEGER:
+		width = dhcp_opt_int_width[code];
+		val = strtoul(str, &end, 0);
+
+		if (*end || buf_len < width)
+			return -1;
+
+		if (width < 4 && val >= (1UL << (width * 8)))
+			return -1;
+
+		for (i = 0; i < width; i++)
+			buf[i] = (val >> ((width - 1 - i) * 8)) & 0xff;
+
+		return width;
+	case DHCP_OPT_STR:
+		slen = strlen(str);
+
+		if (!slen || slen >= buf_len)
+			return -1;
+
+		strncpy((char *)buf, str, buf_len);
+
+		return slen;
+	}
+
+	return -1;
+}
+
 /**
  * struct opt - DHCP option
  * @sent:	Convenience flag, set while filling replies
diff --git a/dhcp.h b/dhcp.h
index cd50c99..3da571c 100644
--- a/dhcp.h
+++ b/dhcp.h
@@ -6,7 +6,24 @@
 #ifndef DHCP_H
 #define DHCP_H
 
+/**
+ * enum dhcp_opt_type - DHCP option value types per RFC 2132
+ * @DHCP_OPT_NONE:	Unsupported or unknown option
+ * @DHCP_OPT_STR:	Variable-length string
+ * @DHCP_OPT_IPV4:	Single IPv4 address
+ * @DHCP_OPT_IPV4_LIST:Multiple IPv4 addresses, comma-separated
+ * @DHCP_OPT_INTEGER:	Unsigned integer (1, 2, or 4 bytes)
+ */
+enum dhcp_opt_type {
+	DHCP_OPT_NONE,
+	DHCP_OPT_STR,
+	DHCP_OPT_IPV4,
+	DHCP_OPT_IPV4_LIST,
+	DHCP_OPT_INTEGER,
+};
+
 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 */
diff --git a/passt.h b/passt.h
index 3a0816f..751fee3 100644
--- a/passt.h
+++ b/passt.h
@@ -184,6 +184,8 @@ struct ip6_ctx {
  * @fqdn:		Guest FQDN
  * @custom_opts:	User-specified DHCP options from --dhcp-opt
  * @custom_opts.code:	DHCP option code
+ * @custom_opts.len:	Length of binary value in @val
+ * @custom_opts.val:	Binary-encoded option value
  * @custom_opts.str:	Original string value from command line
  * @custom_opts_count:	Number of entries in @custom_opts
  * @ifi6:		Template interface for IPv6, -1: none, 0: IPv6 disabled
@@ -271,6 +273,8 @@ struct ctx {
 
 	struct {
 		uint8_t code;
+		uint8_t len;
+		uint8_t val[255];
 		char str[256];
 	} custom_opts[MAX_CUSTOM_DHCP_OPTS];
 	int custom_opts_count;
-- 
2.54.0