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List:       busybox
Subject:    [PATCH 3/5] udhcpc: calculate broadcast address if not given by server
From:       Andreas Oberritter <obi () opendreambox ! org>
Date:       2013-03-20 14:31:25
Message-ID: 1363789887-30252-3-git-send-email-obi () opendreambox ! org
[Download RAW message or body]

* This is more efficient than doing it in the scripts

Signed-off-by: Andreas Oberritter <obi@opendreambox.org>
---
 networking/udhcp/common.h |    2 +-
 networking/udhcp/dhcpc.c  |   17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index 0e8e45f..af8c105 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -126,7 +126,7 @@ enum {
 //#define DHCP_ROOT_PATH        0x11
 //#define DHCP_IP_TTL           0x17
 //#define DHCP_MTU              0x1a
-//#define DHCP_BROADCAST        0x1c
+#define DHCP_BROADCAST          0x1c
 //#define DHCP_ROUTES           0x21
 //#define DHCP_NIS_DOMAIN       0x28
 //#define DHCP_NIS_SERVER       0x29
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 0862288..fe2e681 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -533,6 +533,23 @@ static char **fill_envp(struct dhcp_packet *packet)
 		i++;
 	}
 
+	/* Calculate the broadcast address, if it wasn't provided
+	 * by the server, but a subnet mask of /30 or lower was given.
+	 */
+	if (udhcp_get_option(packet, DHCP_BROADCAST) == NULL) {
+		temp = udhcp_get_option(packet, DHCP_SUBNET);
+		if (temp) {
+			uint32_t subnet;
+			move_from_unaligned32(subnet, temp);
+			if (ntohl(subnet) <= 0xfffffffc) {
+				uint32_t broadcast = packet->yiaddr | ~subnet;
+				*curr = xmalloc(sizeof("broadcast=255.255.255.255"));
+				sprint_nip(*curr, "broadcast=", (uint8_t *)&broadcast);
+				putenv(*curr++);
+			}
+		}
+	}
+
 	return envp;
 }
 
-- 
1.7.10.4

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