DHCPv6: Add support for sending Option 17 (VSIO) (#383)

* DHCP: Add support for sending DHCP option 125 and DHCPv6 Option 17 (VSIO)

Note wireshark doesn't decode option 125 correctly when the it needs to be split into more options if it exceeds 255 bytes.
---------

Signed-off-by: Stipe Poljak (EXT) <[email protected]>
Co-authored-by: Roy Marples <[email protected]>

Author: spoljak-ent

src/dhcp.c

@@ -723,6 +723,76 @@ dhcp_message_add_addr(struct bootp *bootp,
 	return 0;
 }
 
+#ifndef SMALL
+struct rfc3396_ctx {
+	uint8_t code;
+	uint8_t *len;
+	uint8_t **buf;
+	size_t buflen;
+};
+
+/* Encode data as a DHCP Long Option, RFC 3396. */
+/* NOTE: Wireshark does not decode this correctly
+ * when the option overflows the boundary and another option
+ * is created to hold the resta of the data.
+ * Tested against Wireshark-4.4.1 */
+#define RFC3396_BOUNDARY UINT8_MAX
+static ssize_t
+rfc3396_write(struct rfc3396_ctx *ctx, void *data, size_t len)
+{
+	uint8_t *datap = data;
+	size_t wlen, left, r = 0;
+
+	while (len != 0) {
+		if (ctx->len == NULL || *ctx->len == RFC3396_BOUNDARY) {
+			if (ctx->buflen < 2) {
+				errno = ENOMEM;
+				return -1;
+			}
+			*(*ctx->buf)++ = ctx->code;
+			ctx->len = (*ctx->buf)++;
+			*ctx->len = 0;
+			r += 2;
+		}
+
+		wlen = len < RFC3396_BOUNDARY ? len : RFC3396_BOUNDARY;
+		left = RFC3396_BOUNDARY - *ctx->len;
+		if (left < wlen)
+			wlen = left;
+		if (ctx->buflen < wlen) {
+			errno = ENOMEM;
+			return -1;
+		}
+
+		memcpy(*ctx->buf, datap, wlen);
+		datap += wlen;
+		*ctx->buf += wlen;
+		ctx->buflen -= wlen;
+		*ctx->len = (uint8_t)(*ctx->len + wlen);
+		len -= wlen;
+		r += wlen;
+	}
+
+	return (ssize_t)r;
+}
+
+static ssize_t
+rfc3396_write_byte(struct rfc3396_ctx *ctx, uint8_t byte)
+{
+
+	return rfc3396_write(ctx, &byte, sizeof(byte));
+}
+
+static uint8_t *
+rfc3396_zero(struct rfc3396_ctx *ctx) {
+	uint8_t *zerop = *ctx->buf, zero = 0;
+
+	if (rfc3396_write(ctx, &zero, sizeof(zero)) == -1)
+		return NULL;
+	return zerop;
+}
+#endif
+
 static ssize_t
 make_message(struct bootp **bootpm, const struct interface *ifp, uint8_t type)
 {
@@ -1095,6 +1165,50 @@ make_message(struct bootp **bootpm, const struct interface *ifp, uint8_t type)
 			}
 		}
 
+#ifndef SMALL
+		if (ifo->vsio_len &&
+		    !has_option_mask(ifo->nomask, DHO_VIVSO))
+		{
+			struct vsio *vso = ifo->vsio;
+			size_t vlen = ifo->vsio_len;
+			struct vsio_so *so;
+			size_t slen;
+			struct rfc3396_ctx rctx = {
+				.code = DHO_VIVSO,
+				.buf = &p,
+				.buflen = AREA_LEFT,
+			};
+
+			for (; vlen > 0; vso++, vlen--) {
+				if (vso->so_len == 0)
+					continue;
+
+				so = vso->so;
+				slen = vso->so_len;
+
+				ul = htonl(vso->en);
+				if (rfc3396_write(&rctx, &ul, sizeof(ul)) == -1)
+					goto toobig;
+				lp = rfc3396_zero(&rctx);
+				if (lp == NULL)
+					goto toobig;
+
+				for (; slen > 0; so++, slen--) {
+					if (rfc3396_write_byte(&rctx,
+					    (uint8_t)so->opt) == -1)
+						goto toobig;
+					if (rfc3396_write_byte(&rctx,
+					    (uint8_t)so->len) == -1)
+						goto toobig;
+					if (rfc3396_write(&rctx,
+					    so->data, so->len) == -1)
+						goto toobig;
+					*lp = (uint8_t)(*lp + so->len + 2);
+				}
+			}
+		}
+#endif
+
 #ifdef AUTH
 		if ((ifo->auth.options & DHCPCD_AUTH_SENDREQUIRE) !=
 		    DHCPCD_AUTH_SENDREQUIRE &&

src/dhcp6.c

@@ -204,6 +204,11 @@ static int dhcp6_hasprefixdelegation(struct interface *);
 	!((ia)->flags & IPV6_AF_STALE) && \
 	(ia)->prefix_vltime != 0)
 
+
+/* Gets a pointer to the length part of the option to fill it
+ * in later. */
+#define NEXTLEN(p) ((p) + offsetof(struct dhcp6_option, len))
+
 void
 dhcp6_printoptions(const struct dhcpcd_ctx *ctx,
     const struct dhcp_opt *opts, size_t opts_len)
@@ -337,6 +342,74 @@ dhcp6_makevendor(void *data, const struct interface *ifp)
 	return sizeof(o) + len;
 }
 
+#ifndef SMALL
+/* DHCPv6 Option 17 (Vendor-Specific Information Option) */
+static size_t
+dhcp6_makevendoropts(void *data, const struct interface *ifp)
+{
+	uint8_t *p = data, *olenp;
+	const struct if_options *ifo = ifp->options;
+	size_t len = 0, olen;
+	const struct vsio *vsio, *vsio_endp = ifo->vsio6 + ifo->vsio6_len;
+	const struct vsio_so *so, *so_endp;
+	struct dhcp6_option o;
+	uint32_t en;
+	uint16_t opt, slen;
+
+	for (vsio = ifo->vsio6; vsio != vsio_endp; ++vsio) {
+		if (vsio->so_len == 0)
+			continue;
+
+		if (p != NULL) {
+			olenp = NEXTLEN(p);
+			o.code = htons(D6_OPTION_VENDOR_OPTS);
+			o.len = 0;
+			memcpy(p, &o, sizeof(o));
+			p += sizeof(o);
+
+			en = htonl(vsio->en);
+			memcpy(p, &en, sizeof(en));
+			p += sizeof(en);
+		} else
+			olenp = NULL;
+
+		olen = sizeof(en);
+
+		so_endp = vsio->so + vsio->so_len;
+		for (so = vsio->so; so != so_endp; so++) {
+			if (olen + sizeof(opt) + sizeof(slen)
+			    + so->len > UINT16_MAX)
+			{
+				logerrx("%s: option too big", __func__);
+				break;
+			}
+
+			if (p != NULL) {
+				opt = htons(so->opt);
+				memcpy(p, &opt, sizeof(opt));
+				p += sizeof(opt);
+				slen = htons(so->len);
+				memcpy(p, &slen, sizeof(slen));
+				p += sizeof(slen);
+				memcpy(p, so->data, so->len);
+				p += so->len;
+			}
+
+			olen += sizeof(opt) + sizeof(slen) + so->len;
+		}
+
+		if (olenp != NULL) {
+			slen = htons((uint16_t)olen);
+			memcpy(olenp, &slen, sizeof(slen));
+		}
+
+		len += sizeof(o) + olen;
+	}
+
+	return len;
+}
+#endif
+
 static void *
 dhcp6_findoption(void *data, size_t data_len, uint16_t code, uint16_t *len)
 {
@@ -805,6 +878,11 @@ dhcp6_makemessage(struct interface *ifp)
 	if (!has_option_mask(ifo->nomask6, D6_OPTION_VENDOR_CLASS))
 		len += dhcp6_makevendor(NULL, ifp);
 
+#ifndef SMALL
+	if (!has_option_mask(ifo->nomask6, D6_OPTION_VENDOR_OPTS))
+		len += dhcp6_makevendoropts(NULL, ifp);
+#endif
+
 	/* IA */
 	m = NULL;
 	ml = 0;
@@ -950,7 +1028,6 @@ dhcp6_makemessage(struct interface *ifp)
 		p += (_len);			\
 	}					\
 } while (0 /* CONSTCOND */)
-#define NEXTLEN (p + offsetof(struct dhcp6_option, len))
 
 	/* Options are listed in numerical order as per RFC 7844 Section 4.1
 	 * XXX: They should be randomised. */
@@ -968,7 +1045,7 @@ dhcp6_makemessage(struct interface *ifp)
 
 	for (l = 0; IA && l < ifo->ia_len; l++) {
 		ifia = &ifo->ia[l];
-		o_lenp = NEXTLEN;
+		o_lenp = NEXTLEN(p);
 		/* TA structure is the same as the others,
 		 * it just lacks the T1 and T2 timers.
 		 * These happen to be at the end of the struct,
@@ -1064,7 +1141,7 @@ dhcp6_makemessage(struct interface *ifp)
 	    state->send->type != DHCP6_DECLINE &&
 	    n_options)
 	{
-		o_lenp = NEXTLEN;
+		o_lenp = NEXTLEN(p);
 		o.len = 0;
 		COPYIN1(D6_OPTION_ORO, 0);
 		for (l = 0, opt = ifp->ctx->dhcp6_opts;
@@ -1125,11 +1202,16 @@ dhcp6_makemessage(struct interface *ifp)
 	if (!has_option_mask(ifo->nomask6, D6_OPTION_VENDOR_CLASS))
 		p += dhcp6_makevendor(p, ifp);
 
+#ifndef SMALL
+	if (!has_option_mask(ifo->nomask6, D6_OPTION_VENDOR_OPTS))
+		p += dhcp6_makevendoropts(p, ifp);
+#endif
+
 	if (state->send->type != DHCP6_RELEASE &&
 	    state->send->type != DHCP6_DECLINE)
 	{
 		if (fqdn != FQDN_DISABLE) {
-			o_lenp = NEXTLEN;
+			o_lenp = NEXTLEN(p);
 			COPYIN1(D6_OPTION_FQDN, 0);
 			if (hl == 0)
 				*p = D6_FQDN_NONE;

src/dhcpcd.conf.5.in

@@ -24,7 +24,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd October 11, 2024
+.Dd November 1, 2024
 .Dt DHCPCD.CONF 5
 .Os
 .Sh NAME
@@ -766,7 +766,7 @@ It should only be used for Microsoft DHCP servers and the
 should be set to "MSFT 98" or "MSFT 5.0".
 This option is not RFC compliant.
 .It Ic vendor Ar code , Ns Ar value
-Add an encapsulated vendor option.
+Add an encapsulated vendor-specific information option (DHCP Option 43).
 .Ar code
 should be between 1 and 254 inclusive.
 To add a raw vendor string, omit
@@ -782,6 +782,40 @@ Set the vendor option 03 with an IP address as a string.
 .D1 vendor 03,\e"192.168.0.2\e"
 Set un-encapsulated vendor option to hello world.
 .D1 vendor ,"hello world"
+.It Ic vsio Ar en Ar code, Ns Ar value
+Add an encapsulated vendor-specific information option (DHCP Option 125) with
+IANA assigned Enterprise Number
+.Ar en
+proceeding with the
+.Ar code
+which should be between 1 and 255 inclusive, and the
+.Ar value
+after the comma.
+Examples:
+.Pp
+Set the vsio for enterprise number 155 option 01 with an IPv4 address.
+.D1 vsio 155 01,192.168.1.1
+Set the vsio for enterprise number 155 option 02 with a string.
+.D1 vsio 155 02,"hello world"
+Set the vsio for enterprise number 255 option 01 with a hex code.
+.D1 vsio 255 01,01:02:03:04:05
+.It Ic vsio6 Ar en Ar code, Ns Ar value
+Add an encapsulated vendor-specific information option (DHCPv6 Option 17) with
+IANA assigned Enterprise Number
+.Ar en
+proceeding with the
+.Ar code
+which should be between 1 and 65535 inclusive, and the
+.Ar value
+after the comma.
+Examples:
+.Pp
+Set the vsio for enterprise number 155 option 01 with an IPv6 address.
+.D1 vsio6 155 01,2001:0db8:85a3:0000:0000:8a2e:0370:7334
+Set the vsio for enterprise number 155 option 02 with a string.
+.D1 vsio6 155 02,"hello world"
+Set the vsio for enterprise number 255 option 01 with a hex code.
+.D1 vsio6 255 01,01:02:03:04:05
 .It Ic vendorclassid Ar string
 Set the DHCP Vendor Class.
 DHCPv6 has its own option as shown below.