From: Roy Marples <roy@marples.name>
Date: Wed, 9 Jul 2008 22:41:49 +0000 (+0000)
Subject: Ensure that our ARP messages are at least 64 bytes so we're RFC compliant.
X-Git-Tag: v4.0.2~219
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=23d8d9ce8aeac7dd87e3b4b65b929083ab97e7d7;p=thirdparty%2Fdhcpcd.git

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

diff --git a/net.c b/net.c
index fa1b7c92..e6ac96aa 100644
--- 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);