kernel: net: Implement IEEE 802.3 + ARP requests

Introduce IEEE 802.3 related headers such as ones containing the
structure of an ethernet frame as well as its types. This commit
additionally introduces ARP request logic.

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 51 insertions, 38 deletions

diff --git a/sys/include/net/ethertypes.h b/sys/include/net/ethertypes.h
new file mode 100644
index 0000000..753ea10
--- /dev/null
+++ b/sys/include/net/ethertypes.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _NET_ETHERTYPES_H_
+#define _NET_ETHERTYPES_H_
+
+#define ETHERTYPE_IPV4   0x0800
+#define ETHERTYPE_ARP    0x0806
+
+#endif  /* !_NET_ETHERTYPES_H_ */
diff --git a/sys/include/net/if_ether.h b/sys/include/net/if_arp.h
index a8fcfa5..cbfb2fe 100644
--- a/sys/include/net/if_ether.h
+++ b/sys/include/net/if_arp.h
@@ -27,48 +27,25 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef _IF_ETHER_H_
-#define _IF_ETHER_H_
+#ifndef _NETINET_IF_ARP_H_
+#define _NETINET_IF_ARP_H_
 
-#include <sys/cdefs.h>
 #include <sys/types.h>
-#include <net/if.h>
+#include <net/ethertypes.h>
 
-#define MACADDR_LEN 6
+/* ARP hardware types */
+#define ARP_HWTYPE_ETHER 1
 
-struct __packed ether_frame {
-    uint8_t sync[7];        /* Preamble (sync stuff) */
-    uint8_t spd;            /* Start frame delimiter */
-    uint8_t macd[6];        /* MAC destination */
-    uint8_t macs[6];        /* MAC source */
-    uint16_t type;          /* Protocol type */
-    char payload[1];        /* sized @ 1+n */
-};
-
-/*
- * Used by the driver to buffer packets.
- */
-struct etherbuf {
-    struct ether_frame *frp;
-    off_t head;
-    off_t tail;
-    size_t cap;     /* In entries */
-};
+/* ARP operation types */
+#define ARP_REQUEST 1
+#define ARP_REPLY   2
 
-/*
- * Ethernet device
- *
- * if_ether: E
- * driver: D
- *
- * @if_name: Interface name.
- * @tx: Transmit packets (D->E)
- */
-struct etherdev {
-    char if_name[IFNAMESIZ];
-    struct etherbuf *buf;
-    ssize_t(*tx)(struct etherdev *ep, const void *buf, size_t len);
-    char mac_addr[MACADDR_LEN];
+struct arp_hdr {
+    uint16_t hw_type;      /* See ARP_HWTYPE_*  */
+    uint16_t proto_type;   /* See ETHERTYPE_*  */
+    uint8_t hw_len;        /* See ETHER_ADDR_LEN */
+    uint8_t proto_len;     /* Protocol address length */
+    uint16_t op_type;      /* See operation types above */
 };
 
-#endif  /* !_IF_ETHER_H_ */
+#endif  /* !_NETINET_IF_ARP_H_ */