From f41f0416b837925bc8612f45ca58432218ce6707 Mon Sep 17 00:00:00 2001
From: Stefano Brivio <sbrivio@redhat.com>
Date: Fri, 25 Mar 2022 08:32:55 +0100
Subject: [PATCH] dhcp: Minimum option length implied by RFC 951 is 60 bytes,
 not 62

In section 3 ("Packet Format"), "vend" is 64 bytes long, minus the
magic that's 60 bytes, not 62.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 dhcp.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/dhcp.c b/dhcp.c
index 197a515..d24ef86 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -57,6 +57,8 @@ static struct opt opts[255];
 #define DHCPINFORM	8
 #define DHCPFORCERENEW	9
 
+#define OPT_MIN		60 /* RFC 951 */
+
 /**
  * dhcp_init() - Initialise DHCP options
  */
@@ -158,9 +160,9 @@ static int fill(struct msg *m)
 	m->o[offset++] = 255;
 	m->o[offset++] = 0;
 
-	if (offset < 62 /* RFC 951 */) {
-		memset(&m->o[offset], 0, 62 - offset);
-		offset = 62;
+	if (offset < OPT_MIN) {
+		memset(&m->o[offset], 0, OPT_MIN - offset);
+		offset = OPT_MIN;
 	}
 
 	return offset;