Ensure that our ARP messages are at least 64 bytes so we're RFC compliant.

diff --git a/net.c b/net.c
index fa1b7c9284f2da869058be14b8c29424abba6801..e6ac96aa3cebf8469ea795e0360b461d3136f0e2 100644 (file)
--- a/net.c
+++ b/net.c
@@ -618,19 +618,21 @@ int
 send_arp(const struct interface *iface, int op, in_addr_t sip, in_addr_t tip)
 {
        struct arphdr *arp;
-       size_t arpsize;
-       unsigned char *p;
+       size_t arpsize, l;
+       uint8_t *p;
        int retval;
 
        arpsize = sizeof(*arp) + 2 * iface->hwlen + 2 *sizeof(sip);
-
+       /* Ensure that our packet is of the minimum size */
+       if (arpsize < ETHER_MIN_LEN - ETHER_HDR_LEN)
+               arpsize = ETHER_MIN_LEN - ETHER_HDR_LEN;
        arp = xmalloc(arpsize);
        arp->ar_hrd = htons(iface->family);
        arp->ar_pro = htons(ETHERTYPE_IP);
        arp->ar_hln = iface->hwlen;
        arp->ar_pln = sizeof(sip);
        arp->ar_op = htons(op);
-       p = (unsigned char *)arp;
+       p = (uint8_t *)arp;
        p += sizeof(*arp);
        memcpy(p, iface->hwaddr, iface->hwlen);
        p += iface->hwlen;
@@ -641,6 +643,11 @@ send_arp(const struct interface *iface, int op, in_addr_t sip, in_addr_t tip)
        memset(p, 0xff, iface->hwlen);
        p += iface->hwlen;
        memcpy(p, &tip, sizeof(tip));
+       p += sizeof(tip);
+       /* Zero pad if needed */
+       l = p - (uint8_t *)arp;
+       if (l < arpsize)
+               memset(p, 0, arpsize - l);
 
        retval = send_raw_packet(iface, ETHERTYPE_ARP, arp, arpsize);
        free(arp);