[PATCH 2/3] dhcpv6: Add option type table and value parser

[Anshu Kumari <anskuma@redhat.com>]

Add a type table mapping DHCPv6 option codes to value types,
and a parser that encodes CLI strings into the correct binary wire
format for each type.

Supported types: plain string, IPv6 address, IPv6 address list,
8/16/32-bit integers, vendor class (enterprise number + length-prefixed
data, per RFC 8415 Section 21.16), status code (uint16 + message),
and length-prefixed string lists.

Modify dhcpv6_add_option() to call the parser for validation and binary
encoding at configuration time, storing both the raw string and the
encoded value.

Signed-off-by: Anshu Kumari <anskuma@redhat.com>
---
 dhcpv6.c | 228 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 passt.1  |  28 ++++++-
 passt.h  |   4 +
 3 files changed, 255 insertions(+), 5 deletions(-)

diff --git a/dhcpv6.c b/dhcpv6.c
index a0fb77c..85e2926 100644
--- a/dhcpv6.c
+++ b/dhcpv6.c
@@ -25,6 +25,7 @@
 #include <string.h>
 #include <time.h>
 #include <limits.h>
+#include <errno.h>
 
 #include "packet.h"
 #include "util.h"
@@ -32,20 +33,233 @@
 #include "tap.h"
 #include "log.h"
 
+/**
+ * enum dhcpv6_opt_type - DHCPv6 option value types
+ * @DHCPV6_OPT_NONE:		Unsupported or unknown option
+ * @DHCPV6_OPT_STR:		Variable-length string
+ * @DHCPV6_OPT_IPV6:		Single IPv6 address
+ * @DHCPV6_OPT_IPV6_LIST:	Multiple IPv6 addresses, comma-separated
+ * @DHCPV6_OPT_INT8:		Unsigned 8-bit integer
+ * @DHCPV6_OPT_INT16:		Unsigned 16-bit integer
+ * @DHCPV6_OPT_INT32:		Unsigned 32-bit integer
+ * @DHCPV6_OPT_VENDOR_CLASS:	Enterprise number + length-prefixed data
+ * @DHCPV6_OPT_LEN_STR_LIST:	Length-prefixed string list
+ */
+enum dhcpv6_opt_type {
+	DHCPV6_OPT_NONE,
+	DHCPV6_OPT_STR,
+	DHCPV6_OPT_IPV6,
+	DHCPV6_OPT_IPV6_LIST,
+	DHCPV6_OPT_INT8,
+	DHCPV6_OPT_INT16,
+	DHCPV6_OPT_INT32,
+	DHCPV6_OPT_VENDOR_CLASS,
+	DHCPV6_OPT_LEN_STR_LIST,
+};
+
+/**
+ * dhcpv6_opt_types - Maps DHCPv6 option code to value type, indexed by code
+ * RFC 8415 Options: 7, 15, 16, 17, 32, 82, 83
+ * RFC 5970 Options: 59, 60
+ * RFC 4075 Options: 31
+ */
+static const enum dhcpv6_opt_type dhcpv6_opt_types[256] = {
+	[7]   = DHCPV6_OPT_INT8,		/* Preference */
+	[15]  = DHCPV6_OPT_LEN_STR_LIST,	/* User Class */
+	[16]  = DHCPV6_OPT_VENDOR_CLASS,	/* Vendor Class */
+	[17]  = DHCPV6_OPT_VENDOR_CLASS,	/* Vendor Opts */
+	[31]  = DHCPV6_OPT_IPV6_LIST,		/* SNTP Servers */
+	[32]  = DHCPV6_OPT_INT32,		/* Information Refresh Time */
+	[59]  = DHCPV6_OPT_STR,			/* Boot File URL */
+	[60]  = DHCPV6_OPT_LEN_STR_LIST,	/* Boot File Params */
+	[82]  = DHCPV6_OPT_INT32,		/* SOL_MAX_RT */
+	[83]  = DHCPV6_OPT_INT32,		/* INF_MAX_RT */
+};
+
+/**
+ * dhcpv6_opt_parse() - Parse a DHCPv6 option value string into binary
+ * @code:	DHCPv6 option code
+ * @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
+ */
+static int dhcpv6_opt_parse(uint16_t code, const char *str,
+			    uint8_t *buf, size_t buf_len)
+{
+	char chunk[INET6_ADDRSTRLEN];
+	enum dhcpv6_opt_type type;
+	unsigned long val;
+	const char *colon;
+	unsigned int i;
+	uint8_t width;
+	size_t slen;
+	char *end;
+	int len;
+
+	if (!*str)
+		die("Empty value for DHCPv6 option %u", code);
+
+	if (code >= ARRAY_SIZE(dhcpv6_opt_types))
+		die("Unsupported DHCPv6 option: %u,"
+		    " see passt(1) for supported codes", code);
+
+	type = dhcpv6_opt_types[code];
+
+	switch (type) {
+	case DHCPV6_OPT_NONE:
+		die("Unsupported DHCPv6 option: %u,"
+		    " see passt(1) for supported codes", code);
+	case DHCPV6_OPT_IPV6:
+	case DHCPV6_OPT_IPV6_LIST:
+		len = 0;
+
+		while (*str) {
+			slen = strcspn(str, ",");
+			if (!slen || slen >= sizeof(chunk))
+				return -1;
+
+			if (len + (int)sizeof(struct in6_addr) > (int)buf_len)
+				return -1;
+
+			memcpy(chunk, str, slen);
+			chunk[slen] = '\0';
+
+			if (inet_pton(AF_INET6, chunk,
+				      buf + len) != 1)
+				return -1;
+
+			len += sizeof(struct in6_addr);
+
+			if (type == DHCPV6_OPT_IPV6) {
+				if (str[slen] == ',')
+					return -1;
+				break;
+			}
+
+			str += slen;
+			if (*str == ',')
+				str++;
+		}
+
+		if (!len)
+			return -1;
+
+		return len;
+	case DHCPV6_OPT_INT8:
+	case DHCPV6_OPT_INT16:
+	case DHCPV6_OPT_INT32:
+		if (type == DHCPV6_OPT_INT8)
+			width = 1;
+		else if (type == DHCPV6_OPT_INT16)
+			width = 2;
+		else
+			width = 4;
+
+		errno = 0;
+		val = strtoul(str, &end, 0);
+
+		if (*end || errno)
+			return -1;
+
+		if (buf_len < width)
+			return -1;
+
+		if (val >= (1ULL << (width * 8)))
+			return -1;
+
+		for (i = width; i > 0; i--) {
+			buf[i - 1] = val & 0xff;
+			val >>= 8;
+		}
+
+		return width;
+	case DHCPV6_OPT_STR:
+		slen = strlen(str);
+
+		if (!slen || slen >= buf_len)
+			return -1;
+
+		memcpy(buf, str, slen);
+
+		return slen;
+	case DHCPV6_OPT_VENDOR_CLASS:
+		colon = strchr(str, ':');
+		if (!colon)
+			return -1;
+
+		errno = 0;
+		val = strtoul(str, &end, 0);
+		if (end != colon || errno || val > UINT32_MAX)
+			return -1;
+
+		slen = strlen(colon + 1);
+		if (!slen)
+			return -1;
+
+		len = sizeof(uint32_t) + sizeof(uint16_t) + slen;
+		if ((size_t)len > buf_len)
+			return -1;
+
+		uint32_t ent = htonl(val);
+
+		memcpy(buf, &ent, sizeof(ent));
+
+		buf[4] = slen >> 8;
+		buf[5] = slen & 0xff;
+
+		memcpy(buf + sizeof(uint32_t) + sizeof(uint16_t),
+		       colon + 1, slen);
+
+		return len;
+	case DHCPV6_OPT_LEN_STR_LIST:
+		len = 0;
+
+		while (*str) {
+			slen = strcspn(str, ",");
+			if (!slen)
+				return -1;
+
+			if (len + (int)(sizeof(uint16_t) + slen) > (int)buf_len)
+				return -1;
+
+			buf[len]     = slen >> 8;
+			buf[len + 1] = slen & 0xff;
+			len += sizeof(uint16_t);
+
+			memcpy(buf + len, str, slen);
+			len += slen;
+
+			str += slen;
+			if (*str == ',')
+				str++;
+		}
+
+		if (!len)
+			return -1;
+
+		return len;
+	}
+
+	return -1;
+}
+
 /**
  * dhcpv6_add_option() - Add or update a custom DHCPv6 option
  * @c:		Execution context
  * @code:	DHCPv6 option code
  * @val_str:	Value string from command line
  *
- * Stores the option code and raw string value. Binary encoding and
- * injection into DHCPv6 replies are handled by later patches.
+ * Parses @val_str according to the type registered for @code in
+ * dhcpv6_opt_types[]. If @code was already added, the previous value
+ * is overwritten.
  *
  * Return: 0 on success
  */
 int dhcpv6_add_option(struct ctx *c, uint16_t code, const char *val_str)
 {
-	int idx;
+	int idx, ret;
 
 	for (idx = 0; idx < c->custom_v6opts_count; idx++) {
 		if (c->custom_v6opts[idx].code == code)
@@ -59,7 +273,15 @@ int dhcpv6_add_option(struct ctx *c, uint16_t code, const char *val_str)
 		c->custom_v6opts_count++;
 	}
 
+	ret = dhcpv6_opt_parse(code, val_str,
+			       c->custom_v6opts[idx].val,
+			       sizeof(c->custom_v6opts[0].val));
+	if (ret < 0)
+		die("Invalid value for DHCPv6 option %u: %s",
+		    code, val_str);
+
 	c->custom_v6opts[idx].code = code;
+	c->custom_v6opts[idx].len = ret;
 
 	if (snprintf_check(c->custom_v6opts[idx].str,
 			   sizeof(c->custom_v6opts[0].str),
diff --git a/passt.1 b/passt.1
index 9c25214..3c4f3ac 100644
--- a/passt.1
+++ b/passt.1
@@ -433,8 +433,32 @@ Send \fIname\fR as Client FQDN: DHCP option 81 and DHCPv6 option 39.
 .TP
 .BR \-\-dhcpv6-opt " " \fICODE\fR,\fIVALUE\fR
 Set a DHCPv6 option by numeric code. The value format is determined
-automatically from the option code. This option can be specified multiple
-times. If the same option code is given more than once, the last value wins.
+automatically from the option code. Multiple IPv6 addresses are
+comma-separated. This option can be specified multiple times. If the same
+option code is given more than once, the last value wins.
+.RS
+.TP
+.B String options
+59 (Boot File URL, RFC 5970)
+.TP
+.B Length-prefixed string list options (comma-separated entries)
+15 (User Class, RFC 8415), 60 (Boot File Params, RFC 5970).
+Each comma-separated entry is encoded with a 2-byte length prefix.
+Example: \fB\-\-dhcpv6-opt 15,class1,class2\fR.
+.TP
+.B Vendor class options (ENTERPRISE:DATA format)
+16 (Vendor Class, RFC 8415), 17 (Vendor-specific Info, RFC 8415).
+VALUE is \fIENTERPRISE\fR:\fIDATA\fR where \fIENTERPRISE\fR is the IANA
+Private Enterprise Number and \fIDATA\fR is the vendor class string.
+Example: \fB\-\-dhcpv6-opt 16,0:HTTPClient\fR for UEFI HTTP Boot.
+.TP
+.B IPv6 address list options (comma-separated)
+31 (SNTP Servers)
+.TP
+.B Integer options
+7 (Preference, 8-bit), 32 (Information Refresh Time, 32-bit),
+82 (SOL_MAX_RT, 32-bit), 83 (INF_MAX_RT, 32-bit)
+.RE
 
 .TP
 .BR \-t ", " \-\-tcp-ports " " \fIspec
diff --git a/passt.h b/passt.h
index 91509df..21f43d8 100644
--- a/passt.h
+++ b/passt.h
@@ -184,6 +184,8 @@ struct ip6_ctx {
  * @fqdn:		Guest FQDN
  * @custom_v6opts:	User-specified DHCPv6 options from --dhcpv6-opt
  * @custom_v6opts.code:	DHCPv6 option code
+ * @custom_v6opts.len: Length of binary value in @val
+ * @custom_v6opts.val: Binary-encoded option value
  * @custom_v6opts.str:	Original string value from command line
  * @custom_v6opts_count:Number of entries in @custom_v6opts
  * @ifi6:		Template interface for IPv6, -1: none, 0: IPv6 disabled
@@ -271,6 +273,8 @@ struct ctx {
 
 	struct {
 		uint16_t code;
+		uint16_t len;
+		uint8_t val[255];
 		char str[256];
 	} custom_v6opts[MAX_CUSTOM_DHCPV6_OPTS];
 	int custom_v6opts_count;
-- 
2.54.0