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, 95 insertions, 0 deletions

diff --git a/slirp/arp_table.c b/slirp/arp_table.c
new file mode 100644
index 0000000000..820dee22b0
--- /dev/null
+++ b/slirp/arp_table.c
@@ -0,0 +1,95 @@
+/*
+ * ARP table
+ *
+ * Copyright (c) 2011 AdaCore
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "slirp.h"
+
+void arp_table_add(Slirp *slirp, int ip_addr, uint8_t ethaddr[ETH_ALEN])
+{
+    const in_addr_t broadcast_addr =
+        ~slirp->vnetwork_mask.s_addr | slirp->vnetwork_addr.s_addr;
+    ArpTable *arptbl = &slirp->arp_table;
+    int i;
+
+    DEBUG_CALL("arp_table_add");
+    DEBUG_ARG("ip = 0x%x", ip_addr);
+    DEBUG_ARGS((dfd, " hw addr = %02x:%02x:%02x:%02x:%02x:%02x\n",
+                ethaddr[0], ethaddr[1], ethaddr[2],
+                ethaddr[3], ethaddr[4], ethaddr[5]));
+
+    /* Check 0.0.0.0/8 invalid source-only addresses */
+    assert((ip_addr & htonl(~(0xf << 28))) != 0);
+
+    if (ip_addr == 0xffffffff || ip_addr == broadcast_addr) {
+        /* Do not register broadcast addresses */
+        return;
+    }
+
+    /* Search for an entry */
+    for (i = 0; i < ARP_TABLE_SIZE; i++) {
+        if (arptbl->table[i].ar_sip == ip_addr) {
+            /* Update the entry */
+            memcpy(arptbl->table[i].ar_sha, ethaddr, ETH_ALEN);
+            return;
+        }
+    }
+
+    /* No entry found, create a new one */
+    arptbl->table[arptbl->next_victim].ar_sip = ip_addr;
+    memcpy(arptbl->table[arptbl->next_victim].ar_sha,  ethaddr, ETH_ALEN);
+    arptbl->next_victim = (arptbl->next_victim + 1) % ARP_TABLE_SIZE;
+}
+
+bool arp_table_search(Slirp *slirp, int in_ip_addr,
+                      uint8_t out_ethaddr[ETH_ALEN])
+{
+    const in_addr_t broadcast_addr =
+        ~slirp->vnetwork_mask.s_addr | slirp->vnetwork_addr.s_addr;
+    ArpTable *arptbl = &slirp->arp_table;
+    int i;
+
+    DEBUG_CALL("arp_table_search");
+    DEBUG_ARG("ip = 0x%x", in_ip_addr);
+
+    /* Check 0.0.0.0/8 invalid source-only addresses */
+    assert((in_ip_addr & htonl(~(0xf << 28))) != 0);
+
+    /* If broadcast address */
+    if (in_ip_addr == 0xffffffff || in_ip_addr == broadcast_addr) {
+        /* return Ethernet broadcast address */
+        memset(out_ethaddr, 0xff, ETH_ALEN);
+        return 1;
+    }
+
+    for (i = 0; i < ARP_TABLE_SIZE; i++) {
+        if (arptbl->table[i].ar_sip == in_ip_addr) {
+            memcpy(out_ethaddr, arptbl->table[i].ar_sha,  ETH_ALEN);
+            DEBUG_ARGS((dfd, " found hw addr = %02x:%02x:%02x:%02x:%02x:%02x\n",
+                        out_ethaddr[0], out_ethaddr[1], out_ethaddr[2],
+                        out_ethaddr[3], out_ethaddr[4], out_ethaddr[5]));
+            return 1;
+        }
+    }
+
+    return 0;
+}