Don't use the memory of the incoming packet to build the outgoing buffer
as it can be memory of the TX queue in the case of vhost-user.
Moreover with vhost-user, the packet can be split across several
iovec and it's easier to rebuild it in a buffer than updating an
existing iovec array.
Signed-off-by: Laurent Vivier
Reviewed-by: David Gibson
---
arp.c | 84 ++++++++++++++++++++++++++++++++++++++---------------------
1 file changed, 55 insertions(+), 29 deletions(-)
diff --git a/arp.c b/arp.c
index fc482bbd9938..721ff2d529b5 100644
--- a/arp.c
+++ b/arp.c
@@ -31,56 +31,82 @@
#include "tap.h"
/**
- * arp() - Check if this is a supported ARP message, reply as needed
+ * accept_arp() - Check if we should accept this ARP message
* @c: Execution context
- * @p: Packet pool, single packet with Ethernet buffer
+ * @ah: ARP header
+ * @am: ARP message
*
- * Return: 1 if handled, -1 on failure
+ * Return: true if the message is supported, false otherwise.
*/
-int arp(const struct ctx *c, const struct pool *p)
+static bool accept_arp(const struct ctx *c,
+ const struct arphdr *ah, const struct arpmsg *am)
{
- unsigned char swap[4];
- struct ethhdr *eh;
- struct arphdr *ah;
- struct arpmsg *am;
- size_t l2len;
-
- eh = packet_get(p, 0, 0, sizeof(*eh), NULL);
- ah = packet_get(p, 0, sizeof(*eh), sizeof(*ah), NULL);
- am = packet_get(p, 0, sizeof(*eh) + sizeof(*ah), sizeof(*am), NULL);
-
- if (!eh || !ah || !am)
- return -1;
-
if (ah->ar_hrd != htons(ARPHRD_ETHER) ||
ah->ar_pro != htons(ETH_P_IP) ||
ah->ar_hln != ETH_ALEN ||
ah->ar_pln != 4 ||
ah->ar_op != htons(ARPOP_REQUEST))
- return 1;
+ return true;
/* Discard announcements, but not 0.0.0.0 "probes" */
if (memcmp(am->sip, &in4addr_any, sizeof(am->sip)) &&
!memcmp(am->sip, am->tip, sizeof(am->sip)))
- return 1;
+ return true;
/* Don't resolve the guest's assigned address, either. */
if (!memcmp(am->tip, &c->ip4.addr, sizeof(am->tip)))
+ return true;
+
+ return false;
+}
+
+/**
+ * arp() - Check if this is a supported ARP message, reply as needed
+ * @c: Execution context
+ * @p: Packet pool, single packet with Ethernet buffer
+ *
+ * Return: 1 if handled, -1 on failure
+ */
+int arp(const struct ctx *c, const struct pool *p)
+{
+ struct {
+ struct ethhdr eh;
+ struct arphdr ah;
+ struct arpmsg am;
+ } __attribute__((__packed__)) resp;
+ const struct ethhdr *eh;
+ const struct arphdr *ah;
+ const struct arpmsg *am;
+
+ eh = packet_get(p, 0, 0, sizeof(*eh), NULL);
+ ah = packet_get(p, 0, sizeof(*eh), sizeof(*ah), NULL);
+ am = packet_get(p, 0, sizeof(*eh) + sizeof(*ah), sizeof(*am), NULL);
+
+ if (!eh || !ah || !am)
+ return -1;
+
+ if (accept_arp(c, ah, am))
return 1;
- ah->ar_op = htons(ARPOP_REPLY);
- memcpy(am->tha, am->sha, sizeof(am->tha));
- memcpy(am->sha, c->our_tap_mac, sizeof(am->sha));
+ /* Ethernet header */
+ resp.eh.h_proto = htons(ETH_P_ARP);
+ memcpy(resp.eh.h_dest, eh->h_source, sizeof(resp.eh.h_dest));
+ memcpy(resp.eh.h_source, c->our_tap_mac, sizeof(resp.eh.h_source));
- memcpy(swap, am->tip, sizeof(am->tip));
- memcpy(am->tip, am->sip, sizeof(am->tip));
- memcpy(am->sip, swap, sizeof(am->sip));
+ /* ARP header */
+ resp.ah.ar_op = htons(ARPOP_REPLY);
+ resp.ah.ar_hrd = ah->ar_hrd;
+ resp.ah.ar_pro = ah->ar_pro;
+ resp.ah.ar_hln = ah->ar_hln;
+ resp.ah.ar_pln = ah->ar_pln;
- l2len = sizeof(*eh) + sizeof(*ah) + sizeof(*am);
- memcpy(eh->h_dest, eh->h_source, sizeof(eh->h_dest));
- memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source));
+ /* ARP message */
+ memcpy(resp.am.sha, c->our_tap_mac, sizeof(resp.am.sha));
+ memcpy(resp.am.sip, am->tip, sizeof(resp.am.sip));
+ memcpy(resp.am.tha, am->sha, sizeof(resp.am.tha));
+ memcpy(resp.am.tip, am->sip, sizeof(resp.am.tip));
- tap_send_single(c, eh, l2len);
+ tap_send_single(c, &resp, sizeof(resp));
return 1;
}
--
2.49.0