[PATCH 1/3] conf: Add --dhcpv6-opt command-line option

[Anshu Kumari <anskuma@redhat.com>]

Add a --dhcpv6-opt CODE,VALUE option for injecting custom DHCPv6
options into server replies. This patch adds the CLI parsing in conf.c,
storage in struct ctx, and a simple dhcpv6_add_option() that stores the
option code and raw string value.

Signed-off-by: Anshu Kumari <anskuma@redhat.com>
---
 conf.c   | 26 +++++++++++++++++++++++++-
 dhcpv6.c | 37 +++++++++++++++++++++++++++++++++++++
 dhcpv6.h |  1 +
 passt.1  |  6 ++++++
 passt.h  | 12 ++++++++++++
 5 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/conf.c b/conf.c
index 6f86940..ac7e6e5 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 by code\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->custom_v6opts_count; i++)
+			info("    v6 option %u: %s",
+			     c->custom_v6opts[i].code,
+			     c->custom_v6opts[i].str);
 
 dns6:
 		for (i = 0; i < ARRAY_SIZE(c->ip6.dns); i++) {
@@ -1233,6 +1239,7 @@ 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,		34 },
 		{ 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 +1255,13 @@ 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;
 	
@@ -1465,6 +1475,20 @@ 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 34:
+			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 || v6optcode > 255)
+				die("DHCPv6 option code must be 1-255: %s",
+				    optarg);
+
+			dhcpv6_add_option(c, v6optcode, comma + 1);
+			break;
 		case 'd':
 			c->debug = 1;
 			c->quiet = 0;
diff --git a/dhcpv6.c b/dhcpv6.c
index 97c04e2..a0fb77c 100644
--- a/dhcpv6.c
+++ b/dhcpv6.c
@@ -32,6 +32,43 @@
 #include "tap.h"
 #include "log.h"
 
+/**
+ * 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.
+ *
+ * Return: 0 on success
+ */
+int dhcpv6_add_option(struct ctx *c, uint16_t code, const char *val_str)
+{
+	int idx;
+
+	for (idx = 0; idx < c->custom_v6opts_count; idx++) {
+		if (c->custom_v6opts[idx].code == code)
+			break;
+	}
+
+	if (idx == c->custom_v6opts_count) {
+		if (c->custom_v6opts_count >= MAX_CUSTOM_DHCPV6_OPTS)
+			die("Too many --dhcpv6-opt entries (max %d)",
+			    MAX_CUSTOM_DHCPV6_OPTS);
+		c->custom_v6opts_count++;
+	}
+
+	c->custom_v6opts[idx].code = code;
+
+	if (snprintf_check(c->custom_v6opts[idx].str,
+			   sizeof(c->custom_v6opts[0].str),
+			   "%s", val_str))
+		die("DHCPv6 option value too long: %s", val_str);
+
+	return 0;
+}
+
 /**
  * struct opt_hdr - DHCPv6 option header
  * @t:		Option type
diff --git a/dhcpv6.h b/dhcpv6.h
index c706dfd..c01bc36 100644
--- a/dhcpv6.h
+++ b/dhcpv6.h
@@ -9,5 +9,6 @@
 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_add_option(struct ctx *c, uint16_t code, const char *val_str);
 
 #endif /* DHCPV6_H */
diff --git a/passt.1 b/passt.1
index 908fd4a..9c25214 100644
--- a/passt.1
+++ b/passt.1
@@ -430,6 +430,12 @@ 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 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.
+
 .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 1726965..91509df 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
+ * @custom_v6opts:	User-specified DHCPv6 options from --dhcpv6-opt
+ * @custom_v6opts.code:	DHCPv6 option code
+ * @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
  * @ip6:		IPv6 configuration
  * @pasta_ifn:		Name of namespace interface for pasta
@@ -263,6 +267,14 @@ struct ctx {
 	char hostname[PASST_MAXDNAME];
 	char fqdn[PASST_MAXDNAME];
 
+#define MAX_CUSTOM_DHCPV6_OPTS	32
+
+	struct {
+		uint16_t code;
+		char str[256];
+	} custom_v6opts[MAX_CUSTOM_DHCPV6_OPTS];
+	int custom_v6opts_count;
+
 	int ifi6;
 	struct ip6_ctx ip6;
 
-- 
2.54.0