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>
diff --git a/slirp/slirp.c b/slirp/slirp.c
index df787ea..4a9a4d5 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -31,11 +31,11 @@
struct in_addr loopback_addr;
/* emulated hosts use the MAC addr 52:55:IP:IP:IP:IP */
-static const uint8_t special_ethaddr[6] = {
+static const uint8_t special_ethaddr[ETH_ALEN] = {
0x52, 0x55, 0x00, 0x00, 0x00, 0x00
};
-static const uint8_t zero_ethaddr[6] = { 0, 0, 0, 0, 0, 0 };
+static const uint8_t zero_ethaddr[ETH_ALEN] = { 0, 0, 0, 0, 0, 0 };
/* XXX: suppress those select globals */
fd_set *global_readfds, *global_writefds, *global_xfds;
@@ -599,42 +599,8 @@
global_xfds = NULL;
}
-#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));
-
static void arp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
{
- struct ethhdr *eh = (struct ethhdr *)pkt;
struct arphdr *ah = (struct arphdr *)(pkt + ETH_HLEN);
uint8_t arp_reply[max(ETH_HLEN + sizeof(struct arphdr), 64)];
struct ethhdr *reh = (struct ethhdr *)arp_reply;
@@ -645,6 +611,12 @@
ar_op = ntohs(ah->ar_op);
switch(ar_op) {
case ARPOP_REQUEST:
+ if (ah->ar_tip == ah->ar_sip) {
+ /* Gratuitous ARP */
+ arp_table_add(slirp, ah->ar_sip, ah->ar_sha);
+ return;
+ }
+
if ((ah->ar_tip & slirp->vnetwork_mask.s_addr) ==
slirp->vnetwork_addr.s_addr) {
if (ah->ar_tip == slirp->vnameserver_addr.s_addr ||
@@ -657,8 +629,8 @@
return;
arp_ok:
memset(arp_reply, 0, sizeof(arp_reply));
- /* XXX: make an ARP request to have the client address */
- memcpy(slirp->client_ethaddr, eh->h_source, ETH_ALEN);
+
+ arp_table_add(slirp, ah->ar_sip, ah->ar_sha);
/* ARP request for alias/dns mac address */
memcpy(reh->h_dest, pkt + ETH_ALEN, ETH_ALEN);
@@ -679,11 +651,7 @@
}
break;
case ARPOP_REPLY:
- /* reply to request of client mac address ? */
- if (!memcmp(slirp->client_ethaddr, zero_ethaddr, ETH_ALEN) &&
- ah->ar_sip == slirp->client_ipaddr.s_addr) {
- memcpy(slirp->client_ethaddr, ah->ar_sha, ETH_ALEN);
- }
+ arp_table_add(slirp, ah->ar_sip, ah->ar_sha);
break;
default:
break;
@@ -729,15 +697,16 @@
{
uint8_t buf[1600];
struct ethhdr *eh = (struct ethhdr *)buf;
+ uint8_t ethaddr[ETH_ALEN];
+ const struct ip *iph = (const struct ip *)ip_data;
if (ip_data_len + ETH_HLEN > sizeof(buf))
return;
-
- if (!memcmp(slirp->client_ethaddr, zero_ethaddr, ETH_ALEN)) {
+
+ if (!arp_table_search(slirp, iph->ip_dst.s_addr, ethaddr)) {
uint8_t arp_req[ETH_HLEN + sizeof(struct arphdr)];
struct ethhdr *reh = (struct ethhdr *)arp_req;
struct arphdr *rah = (struct arphdr *)(arp_req + ETH_HLEN);
- const struct ip *iph = (const struct ip *)ip_data;
/* If the client addr is not known, there is no point in
sending the packet to it. Normally the sender should have
@@ -765,7 +734,7 @@
slirp->client_ipaddr = iph->ip_dst;
slirp_output(slirp->opaque, arp_req, sizeof(arp_req));
} else {
- memcpy(eh->h_dest, slirp->client_ethaddr, ETH_ALEN);
+ memcpy(eh->h_dest, ethaddr, ETH_ALEN);
memcpy(eh->h_source, special_ethaddr, ETH_ALEN - 4);
/* XXX: not correct */
memcpy(&eh->h_source[2], &slirp->vhost_addr, 4);
