Simple ARP table

This patch adds a simple ARP table in Slirp and also adds handling of
gratuitous ARP requests.

Signed-off-by: Fabien Chouteau <chouteau@adacore.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

1 files changed, 44 insertions, 3 deletions

diff --git a/slirp.h b/slirp.h
index c8b97cf..b1f93c2 100644
--- a/slirp.h
+++ b/slirp.h
@@ -170,6 +170,48 @@ int inet_aton(const char *cp, struct in_addr *ia);
 /* osdep.c */
 int qemu_socket(int domain, int type, int protocol);
 
+#define ETH_ALEN 6
+#define ETH_HLEN 14
+
+#define ETH_P_IP 0x0800 /* Internet Protocol packet  */
+#define ETH_P_ARP 0x0806 /* Address Resolution packet */
+
+#define ARPOP_REQUEST 1 /* ARP request */
+#define ARPOP_REPLY 2 /* ARP reply   */
+
+struct ethhdr {
+    unsigned char h_dest[ETH_ALEN]; /* destination eth addr */
+    unsigned char h_source[ETH_ALEN]; /* source ether addr    */
+    unsigned short h_proto; /* packet type ID field */
+};
+
+struct arphdr {
+    unsigned short ar_hrd; /* format of hardware address */
+    unsigned short ar_pro; /* format of protocol address */
+    unsigned char ar_hln; /* length of hardware address */
+    unsigned char ar_pln; /* length of protocol address */
+    unsigned short ar_op; /* ARP opcode (command)       */
+
+    /*
+     *  Ethernet looks like this : This bit is variable sized however...
+     */
+    unsigned char ar_sha[ETH_ALEN]; /* sender hardware address */
+    uint32_t ar_sip; /* sender IP address       */
+    unsigned char ar_tha[ETH_ALEN]; /* target hardware address */
+    uint32_t ar_tip; /* target IP address       */
+} __attribute__((packed));
+
+#define ARP_TABLE_SIZE 16
+
+typedef struct ArpTable {
+    struct arphdr table[ARP_TABLE_SIZE];
+    int next_victim;
+} ArpTable;
+
+void arp_table_add(Slirp *slirp, int ip_addr, uint8_t ethaddr[ETH_ALEN]);
+
+bool arp_table_search(Slirp *slirp, int in_ip_addr,
+                      uint8_t out_ethaddr[ETH_ALEN]);
 
 struct Slirp {
     QTAILQ_ENTRY(Slirp) entry;
@@ -181,9 +223,6 @@ struct Slirp {
     struct in_addr vdhcp_startaddr;
     struct in_addr vnameserver_addr;
 
-    /* ARP cache for the guest IP addresses (XXX: allow many entries) */
-    uint8_t client_ethaddr[6];
-
     struct in_addr client_ipaddr;
     char client_hostname[33];
 
@@ -227,6 +266,8 @@ struct Slirp {
     char *tftp_prefix;
     struct tftp_session tftp_sessions[TFTP_SESSIONS_MAX];
 
+    ArpTable arp_table;
+
     void *opaque;
 };