Merge remote-tracking branch 'kiszka/queues/slirp' into staging

10 files changed, 241 insertions, 98 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 6115e4ec08..7cbcd7e60d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -431,9 +431,10 @@ S: Maintained
 F: net/
 
 SLIRP
-M: qemu-devel@nongnu.org
-S: Orphan
+M: Jan Kiszka <jan.kiszka@siemens.com>
+S: Maintained
 F: slirp/
+T: git://git.kiszka.org/qemu.git queues/slirp
 
 Usermode Emulation
 ------------------
diff --git a/Makefile.objs b/Makefile.objs
index b6bcfcc169..432b6198e9 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -163,7 +163,7 @@ common-obj-y += qemu-timer.o qemu-timer-common.o
 
 slirp-obj-y = cksum.o if.o ip_icmp.o ip_input.o ip_output.o
 slirp-obj-y += slirp.o mbuf.o misc.o sbuf.o socket.o tcp_input.o tcp_output.o
-slirp-obj-y += tcp_subr.o tcp_timer.o udp.o bootp.o tftp.o
+slirp-obj-y += tcp_subr.o tcp_timer.o udp.o bootp.o tftp.o arp_table.o
 common-obj-$(CONFIG_SLIRP) += $(addprefix slirp/, $(slirp-obj-y))
 
 # xen backend driver support
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;
+}
diff --git a/slirp/bootp.c b/slirp/bootp.c
index 1eb2ed1143..efd1fe777a 100644
--- a/slirp/bootp.c
+++ b/slirp/bootp.c
@@ -149,6 +149,7 @@ static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
     struct in_addr preq_addr;
     int dhcp_msg_type, val;
     uint8_t *q;
+    uint8_t client_ethaddr[ETH_ALEN];
 
     /* extract exact DHCP msg type */
     dhcp_decode(bp, &dhcp_msg_type, &preq_addr);
@@ -164,8 +165,9 @@ static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
     if (dhcp_msg_type != DHCPDISCOVER &&
         dhcp_msg_type != DHCPREQUEST)
         return;
-    /* XXX: this is a hack to get the client mac address */
-    memcpy(slirp->client_ethaddr, bp->bp_hwaddr, 6);
+
+    /* Get client's hardware address from bootp request */
+    memcpy(client_ethaddr, bp->bp_hwaddr, ETH_ALEN);
 
     m = m_get(slirp);
     if (!m) {
@@ -178,25 +180,25 @@ static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
 
     if (dhcp_msg_type == DHCPDISCOVER) {
         if (preq_addr.s_addr != htonl(0L)) {
-            bc = request_addr(slirp, &preq_addr, slirp->client_ethaddr);
+            bc = request_addr(slirp, &preq_addr, client_ethaddr);
             if (bc) {
                 daddr.sin_addr = preq_addr;
             }
         }
         if (!bc) {
          new_addr:
-            bc = get_new_addr(slirp, &daddr.sin_addr, slirp->client_ethaddr);
+            bc = get_new_addr(slirp, &daddr.sin_addr, client_ethaddr);
             if (!bc) {
                 DPRINTF("no address left\n");
                 return;
             }
         }
-        memcpy(bc->macaddr, slirp->client_ethaddr, 6);
+        memcpy(bc->macaddr, client_ethaddr, ETH_ALEN);
     } else if (preq_addr.s_addr != htonl(0L)) {
-        bc = request_addr(slirp, &preq_addr, slirp->client_ethaddr);
+        bc = request_addr(slirp, &preq_addr, client_ethaddr);
         if (bc) {
             daddr.sin_addr = preq_addr;
-            memcpy(bc->macaddr, slirp->client_ethaddr, 6);
+            memcpy(bc->macaddr, client_ethaddr, ETH_ALEN);
         } else {
             daddr.sin_addr.s_addr = 0;
         }
@@ -209,6 +211,9 @@ static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
         }
     }
 
+    /* Update ARP table for this IP address */
+    arp_table_add(slirp, daddr.sin_addr.s_addr, client_ethaddr);
+
     saddr.sin_addr = slirp->vhost_addr;
     saddr.sin_port = htons(BOOTP_SERVER);
 
@@ -218,7 +223,7 @@ static void bootp_reply(Slirp *slirp, const struct bootp_t *bp)
     rbp->bp_xid = bp->bp_xid;
     rbp->bp_htype = 1;
     rbp->bp_hlen = 6;
-    memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);
+    memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, ETH_ALEN);
 
     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
     rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
diff --git a/slirp/if.c b/slirp/if.c
index 0f04e13989..2d79e45bcd 100644
--- a/slirp/if.c
+++ b/slirp/if.c
@@ -6,6 +6,7 @@
  */
 
 #include <slirp.h>
+#include "qemu-timer.h"
 
 #define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))
 
@@ -105,6 +106,9 @@ if_output(struct socket *so, struct mbuf *ifm)
 	ifs_init(ifm);
 	insque(ifm, ifq);
 
+        /* Expiration date = Now + 1 second */
+        ifm->expiration_date = qemu_get_clock_ns(rt_clock) + 1000000000ULL;
+
 diddit:
 	slirp->if_queued++;
 
@@ -153,6 +157,9 @@ diddit:
 void
 if_start(Slirp *slirp)
 {
+    int requeued = 0;
+    uint64_t now;
+
 	struct mbuf *ifm, *ifqt;
 
 	DEBUG_CALL("if_start");
@@ -165,6 +172,8 @@ if_start(Slirp *slirp)
         if (!slirp_can_output(slirp->opaque))
             return;
 
+        now = qemu_get_clock_ns(rt_clock);
+
 	/*
 	 * See which queue to get next packet from
 	 * If there's something in the fastq, select it immediately
@@ -199,11 +208,22 @@ if_start(Slirp *slirp)
 		   ifm->ifq_so->so_nqueued = 0;
 	}
 
-	/* Encapsulate the packet for sending */
-        if_encap(slirp, (uint8_t *)ifm->m_data, ifm->m_len);
-
-        m_free(ifm);
+        if (ifm->expiration_date < now) {
+            /* Expired */
+            m_free(ifm);
+        } else {
+            /* Encapsulate the packet for sending */
+            if (if_encap(slirp, ifm)) {
+                m_free(ifm);
+            } else {
+                /* re-queue */
+                insque(ifm, ifqt);
+                requeued++;
+            }
+        }
 
 	if (slirp->if_queued)
 	   goto again;
+
+        slirp->if_queued = requeued;
 }
diff --git a/slirp/main.h b/slirp/main.h
index 0dd8d81ce4..028df4b361 100644
--- a/slirp/main.h
+++ b/slirp/main.h
@@ -42,5 +42,5 @@ extern int tcp_keepintvl;
 #define PROTO_PPP 0x2
 #endif
 
-void if_encap(Slirp *slirp, const uint8_t *ip_data, int ip_data_len);
+int if_encap(Slirp *slirp, struct mbuf *ifm);
 ssize_t slirp_send(struct socket *so, const void *buf, size_t len, int flags);
diff --git a/slirp/mbuf.c b/slirp/mbuf.c
index ce2eb843f5..c699c75096 100644
--- a/slirp/mbuf.c
+++ b/slirp/mbuf.c
@@ -70,6 +70,8 @@ m_get(Slirp *slirp)
 	m->m_len = 0;
         m->m_nextpkt = NULL;
         m->m_prevpkt = NULL;
+        m->arp_requested = false;
+        m->expiration_date = (uint64_t)-1;
 end_error:
 	DEBUG_ARG("m = %lx", (long )m);
 	return m;
diff --git a/slirp/mbuf.h b/slirp/mbuf.h
index b74544b42b..55170e517b 100644
--- a/slirp/mbuf.h
+++ b/slirp/mbuf.h
@@ -86,6 +86,8 @@ struct mbuf {
 		char	m_dat_[1]; /* ANSI don't like 0 sized arrays */
 		char	*m_ext_;
 	} M_dat;
+    bool     arp_requested;
+    uint64_t expiration_date;
 };
 
 #define m_next		m_hdr.mh_next
diff --git a/slirp/slirp.c b/slirp/slirp.c
index df787ea1d9..a86cc6eb2d 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 @@ void slirp_select_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds,
 	 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 @@ static void arp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
     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 @@ static void arp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
             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 @@ static void arp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
         }
         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;
@@ -724,54 +692,63 @@ void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
     }
 }
 
-/* output the IP packet to the ethernet device */
-void if_encap(Slirp *slirp, const uint8_t *ip_data, int ip_data_len)
+/* Output the IP packet to the ethernet device. Returns 0 if the packet must be
+ * re-queued.
+ */
+int if_encap(Slirp *slirp, struct mbuf *ifm)
 {
     uint8_t buf[1600];
     struct ethhdr *eh = (struct ethhdr *)buf;
+    uint8_t ethaddr[ETH_ALEN];
+    const struct ip *iph = (const struct ip *)ifm->m_data;
 
-    if (ip_data_len + ETH_HLEN > sizeof(buf))
-        return;
-    
-    if (!memcmp(slirp->client_ethaddr, zero_ethaddr, ETH_ALEN)) {
+    if (ifm->m_len + ETH_HLEN > sizeof(buf)) {
+        return 1;
+    }
+
+    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
-           done an ARP request to get its MAC address. Here we do it
-           in place of sending the packet and we hope that the sender
-           will retry sending its packet. */
-        memset(reh->h_dest, 0xff, ETH_ALEN);
-        memcpy(reh->h_source, special_ethaddr, ETH_ALEN - 4);
-        memcpy(&reh->h_source[2], &slirp->vhost_addr, 4);
-        reh->h_proto = htons(ETH_P_ARP);
-        rah->ar_hrd = htons(1);
-        rah->ar_pro = htons(ETH_P_IP);
-        rah->ar_hln = ETH_ALEN;
-        rah->ar_pln = 4;
-        rah->ar_op = htons(ARPOP_REQUEST);
-        /* source hw addr */
-        memcpy(rah->ar_sha, special_ethaddr, ETH_ALEN - 4);
-        memcpy(&rah->ar_sha[2], &slirp->vhost_addr, 4);
-        /* source IP */
-        rah->ar_sip = slirp->vhost_addr.s_addr;
-        /* target hw addr (none) */
-        memset(rah->ar_tha, 0, ETH_ALEN);
-        /* target IP */
-        rah->ar_tip = iph->ip_dst.s_addr;
-        slirp->client_ipaddr = iph->ip_dst;
-        slirp_output(slirp->opaque, arp_req, sizeof(arp_req));
+
+        if (!ifm->arp_requested) {
+            /* If the client addr is not known, send an ARP request */
+            memset(reh->h_dest, 0xff, ETH_ALEN);
+            memcpy(reh->h_source, special_ethaddr, ETH_ALEN - 4);
+            memcpy(&reh->h_source[2], &slirp->vhost_addr, 4);
+            reh->h_proto = htons(ETH_P_ARP);
+            rah->ar_hrd = htons(1);
+            rah->ar_pro = htons(ETH_P_IP);
+            rah->ar_hln = ETH_ALEN;
+            rah->ar_pln = 4;
+            rah->ar_op = htons(ARPOP_REQUEST);
+
+            /* source hw addr */
+            memcpy(rah->ar_sha, special_ethaddr, ETH_ALEN - 4);
+            memcpy(&rah->ar_sha[2], &slirp->vhost_addr, 4);
+
+            /* source IP */
+            rah->ar_sip = slirp->vhost_addr.s_addr;
+
+            /* target hw addr (none) */
+            memset(rah->ar_tha, 0, ETH_ALEN);
+
+            /* target IP */
+            rah->ar_tip = iph->ip_dst.s_addr;
+            slirp->client_ipaddr = iph->ip_dst;
+            slirp_output(slirp->opaque, arp_req, sizeof(arp_req));
+            ifm->arp_requested = true;
+        }
+        return 0;
     } 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);
         eh->h_proto = htons(ETH_P_IP);
-        memcpy(buf + sizeof(struct ethhdr), ip_data, ip_data_len);
-        slirp_output(slirp->opaque, buf, ip_data_len + ETH_HLEN);
+        memcpy(buf + sizeof(struct ethhdr), ifm->m_data, ifm->m_len);
+        slirp_output(slirp->opaque, buf, ifm->m_len + ETH_HLEN);
+        return 1;
     }
 }
 
diff --git a/slirp/slirp.h b/slirp/slirp.h
index 16bb6bae45..2a070e6126 100644
--- a/slirp/slirp.h
+++ b/slirp/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;
 };