use the same option list for dhcp discovery and request

The DHCP client is supposed to use the same option request list for
both DHCP discovery and request.

This will also allow us to fill the list in single function.

Reviewed by:	bapt
Differential Revision:	https://reviews.freebsd.org/D10981

lib/libstand/bootp.c

@@ -93,6 +93,35 @@ struct in_addr dhcp_serverip;
 struct bootp *bootp_response;
 size_t bootp_response_size;
 
+static void
+bootp_fill_request(unsigned char *bp_vend)
+{
+	/*
+	 * We are booting from PXE, we want to send the string
+	 * 'PXEClient' to the DHCP server so you have the option of
+	 * only responding to PXE aware dhcp requests.
+	 */
+	bp_vend[0] = TAG_CLASSID;
+	bp_vend[1] = 9;
+	bcopy("PXEClient", &bp_vend[2], 9);
+	bp_vend[11] = TAG_USER_CLASS;
+	/* len of each user class + number of user class */
+	bp_vend[12] = 8;
+	/* len of the first user class */
+	bp_vend[13] = 7;
+	bcopy("FreeBSD", &bp_vend[14], 7);
+	bp_vend[21] = TAG_PARAM_REQ;
+	bp_vend[22] = 7;
+	bp_vend[23] = TAG_ROOTPATH;
+	bp_vend[24] = TAG_HOSTNAME;
+	bp_vend[25] = TAG_SWAPSERVER;
+	bp_vend[26] = TAG_GATEWAY;
+	bp_vend[27] = TAG_SUBNET_MASK;
+	bp_vend[28] = TAG_INTF_MTU;
+	bp_vend[29] = TAG_SERVERID;
+	bp_vend[30] = TAG_END;
+}
+
 /* Fetch required bootp infomation */
 void
 bootp(int sock)
@@ -136,31 +165,8 @@ bootp(int sock)
 	bp->bp_vend[4] = TAG_DHCP_MSGTYPE;
 	bp->bp_vend[5] = 1;
 	bp->bp_vend[6] = DHCPDISCOVER;
+	bootp_fill_request(&bp->bp_vend[7]);
 
-	/*
-	 * We are booting from PXE, we want to send the string
-	 * 'PXEClient' to the DHCP server so you have the option of
-	 * only responding to PXE aware dhcp requests.
-	 */
-	bp->bp_vend[7] = TAG_CLASSID;
-	bp->bp_vend[8] = 9;
-	bcopy("PXEClient", &bp->bp_vend[9], 9);
-	bp->bp_vend[18] = TAG_USER_CLASS;
-	/* len of each user class + number of user class */
-	bp->bp_vend[19] = 8;
-	/* len of the first user class */
-	bp->bp_vend[20] = 7;
-	bcopy("FreeBSD", &bp->bp_vend[21], 7);
-	bp->bp_vend[28] = TAG_PARAM_REQ;
-	bp->bp_vend[29] = 7;
-	bp->bp_vend[30] = TAG_ROOTPATH;
-	bp->bp_vend[31] = TAG_HOSTNAME;
-	bp->bp_vend[32] = TAG_SWAPSERVER;
-	bp->bp_vend[33] = TAG_GATEWAY;
-	bp->bp_vend[34] = TAG_SUBNET_MASK;
-	bp->bp_vend[35] = TAG_INTF_MTU;
-	bp->bp_vend[36] = TAG_SERVERID;
-	bp->bp_vend[37] = TAG_END;
 #else
 	bp->bp_vend[4] = TAG_END;
 #endif
@@ -196,10 +202,7 @@ bootp(int sock)
 		bp->bp_vend[20] = 4;
 		leasetime = htonl(300);
 		bcopy(&leasetime, &bp->bp_vend[21], 4);
-		bp->bp_vend[25] = TAG_CLASSID;
-		bp->bp_vend[26] = 9;
-		bcopy("PXEClient", &bp->bp_vend[27], 9);
-		bp->bp_vend[36] = TAG_END;
+		bootp_fill_request(&bp->bp_vend[25]);
 
 		expected_dhcpmsgtype = DHCPACK;