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-rw-r--r--com32/lib/dhcppack.c166
1 files changed, 166 insertions, 0 deletions
diff --git a/com32/lib/dhcppack.c b/com32/lib/dhcppack.c
new file mode 100644
index 00000000..a08583c4
--- /dev/null
+++ b/com32/lib/dhcppack.c
@@ -0,0 +1,166 @@
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+// #include <arpa/inet.h>
+#include <netinet/in.h>
+
+// #include "dhcp.h"
+#include <dhcp.h>
+
+/*
+ * Pack DHCP options into an option field, without overload support.
+ * On return, len contains the number of active bytes, and the full
+ * field is zero-padded.
+ *
+ * Options which are successfully placed have their length zeroed out.
+ */
+static int dhcp_pack_field_zero(void *field, size_t *len,
+ struct dhcp_option opt[256])
+{
+ int i;
+ size_t xlen, plen;
+ const uint8_t *p;
+ uint8_t *q = field;
+ size_t spc = *len;
+ int err = 0;
+
+ if (!*len)
+ return ENOSPC;
+
+ for (i = 1; i < 255; i++) {
+ if (opt[i].len < 0)
+ continue;
+
+ /* We need to handle the 0 case as well as > 255 */
+ if (opt[i].len <= 255)
+ xlen = opt[i].len + 2;
+ else
+ xlen = opt[i].len + 2*((opt[i].len+254)/255);
+
+ p = opt[i].data;
+
+ if (xlen >= spc) {
+ /* This option doesn't fit... */
+ err++;
+ continue;
+ }
+
+ xlen = opt[i].len;
+ do {
+ *q++ = i;
+ *q++ = plen = xlen > 255 ? 255 : xlen;
+ if (plen)
+ memcpy(q, p, plen);
+ q += plen;
+ p += plen;
+ spc -= plen+2;
+ xlen -= plen;
+ } while (xlen);
+
+ opt[i].len = -1;
+ }
+
+ *q++ = 255; /* End marker */
+ memset(q, 0, spc); /* Zero-pad the rest of the field */
+
+ *len = xlen = q - (uint8_t *)field;
+ return err;
+}
+
+/*
+ * Pack DHCP options into an option field, without overload support.
+ * On return, len contains the number of active bytes, and the full
+ * field is zero-padded.
+ *
+ * Use this to encode encapsulated option fields.
+ */
+int dhcp_pack_field(void *field, size_t *len,
+ struct dhcp_option opt[256])
+{
+ struct dhcp_option ox[256];
+
+ memcpy(ox, opt, sizeof ox);
+ return dhcp_pack_field_zero(field, len, ox);
+}
+
+/*
+ * Pack DHCP options into a packet.
+ * Apply overloading if (and only if) the "file" or "sname" option
+ * doesn't fit in the respective dedicated fields.
+ */
+int dhcp_pack_packet(void *packet, size_t *len,
+ const struct dhcp_option opt[256])
+{
+ struct dhcp_packet *pkt = packet;
+ size_t spc = *len;
+ uint8_t overload;
+ struct dhcp_option ox[256];
+ uint8_t *q;
+ int err;
+
+ if (spc < sizeof(struct dhcp_packet))
+ return ENOSPC; /* Buffer impossibly small */
+
+ pkt->magic = htonl(DHCP_VENDOR_MAGIC);
+
+ memcpy(ox, opt, sizeof ox);
+
+ /* Figure out if we should do overloading or not */
+ overload = 0;
+
+ if (opt[67].len > 128)
+ overload |= 1;
+ else
+ ox[67].len = -1;
+
+ if (opt[66].len > 64)
+ overload |= 2;
+ else
+ ox[66].len = -1;
+
+ /* Kill any passed-in overload option */
+ ox[52].len = -1;
+
+ q = pkt->options;
+ spc -= 240;
+
+ /* Force option 53 (DHCP packet type) first */
+ if (ox[53].len == 1) {
+ *q++ = 53;
+ *q++ = 1;
+ *q++ = *(uint8_t *)ox[53].data;
+ spc -= 3;
+ ox[53].len = -1;
+ }
+
+ /* Follow with the overload option, if applicable */
+ if (overload) {
+ *q++ = 52;
+ *q++ = 1;
+ *q++ = overload;
+ spc -= 3;
+ }
+
+ err = dhcp_pack_field_zero(q, &spc, ox);
+ *len = spc + (q-(uint8_t *)packet);
+
+ if (overload & 1) {
+ spc = 128;
+ err = dhcp_pack_field_zero(pkt->file, &spc, ox);
+ } else {
+ memset(pkt->file, 0, 128);
+ if (opt[67].len > 0)
+ memcpy(pkt->file, opt[67].data, opt[67].len);
+ }
+
+ if (overload & 2) {
+ spc = 64;
+ err = dhcp_pack_field_zero(pkt->sname, &spc, ox);
+ } else {
+ memset(pkt->sname, 0, 64);
+ if (opt[66].len > 0)
+ memcpy(pkt->sname, opt[66].data, opt[66].len);
+ }
+
+ return err;
+}