[PATCH v2 1/2] dhcpv6: Add --dhcpv6-opt with option type table and value parser

[Anshu Kumari <anskuma@redhat.com>]

Introduce the --dhcpv6-opt flag that allows setting arbitrary DHCPv6
options from command-line in the form [--dhcpv6-opt CODE,VALUE].

Add a type lookup table mapping option codes to value types (IPv6,
IPv6 list, integer, string, vendor class, length-prefixed string
list) and dhcpv6_opt_parse() to convert CLI strings to binary wire
format. If the same option code is given more than once, the
last value wins.

Link: https://bugs.passt.top/show_bug.cgi?id=192
Signed-off-by: Anshu Kumari <anskuma@redhat.com>
---
v2:
  - Renamed custom_v6opts to dhcpv6_opts, MAX_CUSTOM_DHCPV6_OPTS
    to MAX_DHCPV6_OPTS.
  - Dropped val/len from ctx struct.
  - Moved dhcpv6_add_option() to conf.c as static
    conf_dhcpv6_option().
  - Made dhcpv6_opt_parse() non-static, declared in dhcpv6.h
  - Omitted explicit [256] from dhcpv6_opt_types[].
  - Moved chunk declaration into while block.
  - Removed redundant !slen check in DHCPV6_OPT_STR case.
  - All errors in dhcpv6_opt_parse() return -1, removed die()
    calls.
---
 conf.c   |  60 +++++++++++++++-
 dhcpv6.c | 209 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 dhcpv6.h |   2 +
 passt.1  |  31 +++++++++
 passt.h  |  12 ++++
 5 files changed, 313 insertions(+), 1 deletion(-)

diff --git a/conf.c b/conf.c
index cd05adf..3981c1b 100644
--- a/conf.c
+++ b/conf.c
@@ -47,6 +47,7 @@
 #include "lineread.h"
 #include "isolation.h"
 #include "log.h"
+#include "dhcpv6.h"
 #include "vhost_user.h"
 #include "epoll_ctl.h"
 #include "conf.h"
@@ -616,7 +617,8 @@ static void usage(const char *name, FILE *f, int status)
 		"  -S, --search LIST	Space-separated list, search domains\n"
 		"    a single, empty option disables the DNS search list\n"
 		"  -H, --hostname NAME 	Hostname to configure client with\n"
-		"  --fqdn NAME		FQDN to configure client with\n");
+		"  --fqdn NAME		FQDN to configure client with\n"
+		"  --dhcpv6-opt CODE,VAL	Set DHCPv6 option CODE to VAL\n");
 	if (strstr(name, "pasta"))
 		FPRINTF(f, "    default: don't use any search list\n");
 	else
@@ -884,6 +886,10 @@ static void conf_print(const struct ctx *c)
 		info("    our link-local: %s",
 		     inet_ntop(AF_INET6, &c->ip6.our_tap_ll,
 			       buf, sizeof(buf)));
+		for (i = 0; i < c->dhcpv6_opts_count; i++)
+			info("    v6 option %u: %s",
+			     c->dhcpv6_opts[i].code,
+			     c->dhcpv6_opts[i].str);
 
 dns6:
 		for (i = 0; i < ARRAY_SIZE(c->ip6.dns); i++) {
@@ -1150,6 +1156,41 @@ static void conf_sock_listen(const struct ctx *c)
 		die_perror("Couldn't add configuration socket to epoll");
 }
 
+/**
+ * conf_dhcpv6_option() - Set value for a DHCPv6 option in configuration
+ * @c:		Execution context
+ * @code:	DHCPv6 option code
+ * @val_str:	Value string from command line
+ */
+static void conf_dhcpv6_option(struct ctx *c, uint16_t code,
+			       const char *val_str)
+{
+	uint8_t tmp[255];
+	int idx;
+
+	if (dhcpv6_opt_parse(code, val_str, tmp, sizeof(tmp)) < 0)
+		die("Invalid value for DHCPv6 option %u: %s", code, val_str);
+
+	for (idx = 0; idx < c->dhcpv6_opts_count; idx++) {
+		if (c->dhcpv6_opts[idx].code == code)
+			break;
+	}
+
+	if (idx == c->dhcpv6_opts_count) {
+		if (c->dhcpv6_opts_count >= MAX_DHCPV6_OPTS)
+			die("Too many --dhcpv6-opt entries (max %d)",
+			    MAX_DHCPV6_OPTS);
+		c->dhcpv6_opts_count++;
+	}
+
+	c->dhcpv6_opts[idx].code = code;
+
+	if (snprintf_check(c->dhcpv6_opts[idx].str,
+			   sizeof(c->dhcpv6_opts[0].str),
+			   "%s", val_str))
+		die("DHCPv6 option value too long: %s", val_str);
+}
+
 /**
  * conf() - Process command-line arguments and set configuration
  * @c:		Execution context
@@ -1233,6 +1274,7 @@ void conf(struct ctx *c, int argc, char **argv)
 		{"migrate-no-linger", no_argument,	NULL,		30 },
 		{"stats", required_argument,		NULL,		31 },
 		{"conf-path",	required_argument,	NULL,		'c' },
+		{"dhcpv6-opt", required_argument,	NULL,		35 },
 		{ 0 },
 	};
 	const char *optstring = "+dqfel:hs:c:F:I:p:P:m:a:n:M:g:i:o:D:S:H:461t:u:T:U:";
@@ -1248,10 +1290,13 @@ void conf(struct ctx *c, int argc, char **argv)
 	uint8_t prefix_len_from_opt = 0;
 	unsigned int ifi4 = 0, ifi6 = 0;
 	const char *logfile = NULL;
+	unsigned long v6optcode;
 	char *runas = NULL;
 	size_t logsize = 0;
+	const char *comma;
 	long fd_tap_opt;
 	int name, ret;
+	char *end;
 	uid_t uid;
 	gid_t gid;
 
@@ -1467,6 +1512,19 @@ void conf(struct ctx *c, int argc, char **argv)
 				die("Can't display statistics if not running in foreground");
 			c->stats = strtol(optarg, NULL, 0);
 			break;
+		case 35:
+			comma = strchr(optarg, ',');
+			if (!comma)
+				die("--dhcpv6-opt requires CODE,VALUE format");
+
+			errno = 0;
+			v6optcode = strtoul(optarg, &end, 0);
+			if (end != comma || errno || v6optcode < 1)
+				die("Invalid DHCPv6 option code: %s",
+				    optarg);
+
+			conf_dhcpv6_option(c, v6optcode, comma + 1);
+			break;
 		case 'd':
 			c->debug = 1;
 			c->quiet = 0;
diff --git a/dhcpv6.c b/dhcpv6.c
index 97c04e2..1e1dd0d 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"
@@ -278,6 +279,214 @@ static struct resp_not_on_link_t {
 	{ 0, },
 };
 
+/**
+ * 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[] = {
+	[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
+ */
+int dhcpv6_opt_parse(uint16_t code, const char *str,
+		     uint8_t *buf, size_t buf_len)
+{
+	enum dhcpv6_opt_type type;
+	unsigned long val;
+	unsigned int i;
+	uint8_t width;
+	size_t slen;
+	char *end;
+	int len;
+
+	if (!*str)
+		return -1;
+
+	if (code >= ARRAY_SIZE(dhcpv6_opt_types))
+		return -1;
+
+	type = dhcpv6_opt_types[code];
+
+	switch (type) {
+	case DHCPV6_OPT_NONE:
+		return -1;
+	case DHCPV6_OPT_IPV6:
+	case DHCPV6_OPT_IPV6_LIST:
+		len = 0;
+
+		while (*str) {
+			char chunk[INET6_ADDRSTRLEN];
+			size_t clen;
+
+			clen = strcspn(str, ",");
+			if (!clen || clen >= sizeof(chunk))
+				return -1;
+
+			if (len + (int)sizeof(struct in6_addr) > (int)buf_len)
+				return -1;
+
+			memcpy(chunk, str, clen);
+			chunk[clen] = '\0';
+
+			if (inet_pton(AF_INET6, chunk, buf + len) != 1)
+				return -1;
+
+			len += sizeof(struct in6_addr);
+
+			if (type == DHCPV6_OPT_IPV6) {
+				if (str[clen] == ',')
+					return -1;
+				break;
+			}
+
+			str += clen + (str[clen] == ',');
+		}
+
+		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;
+
+		if (buf_len < width)
+			return -1;
+
+		errno = 0;
+		val = strtoul(str, &end, 0);
+
+		if (*end || errno || 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 >= buf_len)
+			return -1;
+
+		memcpy(buf, str, slen);
+
+		return slen;
+	case DHCPV6_OPT_VENDOR_CLASS: {
+		const char *colon;
+		uint32_t ent;
+
+		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;
+
+		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_opt() - Get option from DHCPv6 message
  * @data:	Buffer with options, set to matching option on return
diff --git a/dhcpv6.h b/dhcpv6.h
index c706dfd..2da1c76 100644
--- a/dhcpv6.h
+++ b/dhcpv6.h
@@ -9,5 +9,7 @@
 int dhcpv6(struct ctx *c, struct iov_tail *data,
 	   struct in6_addr *saddr, struct in6_addr *daddr);
 void dhcpv6_init(const struct ctx *c);
+int dhcpv6_opt_parse(uint16_t code, const char *str,
+		     uint8_t *buf, size_t buf_len);
 
 #endif /* DHCPV6_H */
diff --git a/passt.1 b/passt.1
index 908fd4a..0f771cb 100644
--- a/passt.1
+++ b/passt.1
@@ -430,6 +430,37 @@ Send \fIname\fR as DHCP option 12 (hostname).
 FQDN to configure the client with.
 Send \fIname\fR as Client FQDN: DHCP option 81 and DHCPv6 option 39.
 
+.TP
+.BR \-\-dhcpv6-opt " " \fICODE\fR,\fIVALUE\fR
+Set DHCPv6 option \fICODE\fR to \fIVALUE\fR.  The value format depends
+on the option type and is determined 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
 Configure TCP port forwarding to guest or namespace. \fIspec\fR can be one of:
diff --git a/passt.h b/passt.h
index 3a07294..8f4ddef 100644
--- a/passt.h
+++ b/passt.h
@@ -182,6 +182,10 @@ struct ip6_ctx {
  * @dns_search:		DNS search list
  * @hostname:		Guest hostname
  * @fqdn:		Guest FQDN
+ * @dhcpv6_opts:	User-specified DHCPv6 options from --dhcpv6-opt
+ * @dhcpv6_opts.code:	DHCPv6 option code
+ * @dhcpv6_opts.str:	String value from command line
+ * @dhcpv6_opts_count:	Number of entries in @dhcpv6_opts
  * @ifi6:		Template interface for IPv6, -1: none, 0: IPv6 disabled
  * @ip6:		IPv6 configuration
  * @pasta_ifn:		Name of namespace interface for pasta
@@ -264,6 +268,14 @@ struct ctx {
 	char hostname[PASST_MAXDNAME];
 	char fqdn[PASST_MAXDNAME];
 
+#define MAX_DHCPV6_OPTS	32
+
+	struct {
+		uint16_t code;
+		char str[255];
+	} dhcpv6_opts[MAX_DHCPV6_OPTS];
+	int dhcpv6_opts_count;
+
 	int ifi6;
 	struct ip6_ctx ip6;
 
-- 
2.54.0