+int dhcp_option_append(DHCPMessage *message, size_t size, size_t *offset,
+ uint8_t overload,
+ uint8_t code, size_t optlen, const void *optval) {
+ size_t file_offset = 0, sname_offset =0;
+ bool file, sname;
+ int r;
+
+ assert(message);
+ assert(offset);
+
+ file = overload & DHCP_OVERLOAD_FILE;
+ sname = overload & DHCP_OVERLOAD_SNAME;
+
+ if (*offset < size) {
+ /* still space in the options array */
+ r = option_append(message->options, size, offset, code, optlen, optval);
+ if (r >= 0)
+ return 0;
+ else if (r == -ENOBUFS && (file || sname)) {
+ /* did not fit, but we have more buffers to try
+ close the options array and move the offset to its end */
+ r = option_append(message->options, size, offset, DHCP_OPTION_END, 0, NULL);
+ if (r < 0)
+ return r;
+
+ *offset = size;
+ } else
+ return r;
+ }
+
+ if (overload & DHCP_OVERLOAD_FILE) {
+ file_offset = *offset - size;
+
+ if (file_offset < sizeof(message->file)) {
+ /* still space in the 'file' array */
+ r = option_append(message->file, sizeof(message->file), &file_offset, code, optlen, optval);
+ if (r >= 0) {
+ *offset = size + file_offset;
+ return 0;
+ } else if (r == -ENOBUFS && sname) {
+ /* did not fit, but we have more buffers to try
+ close the file array and move the offset to its end */
+ r = option_append(message->options, size, offset, DHCP_OPTION_END, 0, NULL);
+ if (r < 0)
+ return r;
+
+ *offset = size + sizeof(message->file);
+ } else
+ return r;
+ }
+ }
+
+ if (overload & DHCP_OVERLOAD_SNAME) {
+ sname_offset = *offset - size - (file ? sizeof(message->file) : 0);
+
+ if (sname_offset < sizeof(message->sname)) {
+ /* still space in the 'sname' array */
+ r = option_append(message->sname, sizeof(message->sname), &sname_offset, code, optlen, optval);
+ if (r >= 0) {
+ *offset = size + (file ? sizeof(message->file) : 0) + sname_offset;
+ return 0;
+ } else {
+ /* no space, or other error, give up */
+ return r;
+ }
+ }
+ }
+
+ return -ENOBUFS;
+}
+