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netutils/dhcpc: Set BOOTP BROADCAST flag when IPFORWARD is enabled

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Socket binded to INADDR_ANY is not intended to receive unicast traffic before being fully configured, at least dhclient configured with socket-only won't do so on Linux and BSDs (https://github.com/isc-projects/dhcp/blob/v4_4_3/common/socket.c#L1201).
We can sometimes receive unicast traffic before being fully configured, it's good, but not always, so we need to set the broadcast flag under some situations.

Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
This commit is contained in:
Zhe Weng 2023-06-12 16:18:41 +08:00 committed by Xiang Xiao
parent 400951b7de
commit 3e68694bdf
2 changed files with 12 additions and 6 deletions
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7
netutils/dhcpc/Kconfig
View File

@ -32,10 +32,15 @@ config NETUTILS_DHCPC_RETRIES
config NETUTILS_DHCPC_BOOTP_FLAGS
hex "Flags of Bootstrap"
default 0x0000
default 0x0000 if !NET_IPFORWARD
default 0x8000 if NET_IPFORWARD
---help---
This setting to set the BOOTP broadcast flags.
Reference RFC1542: Clarifications and Extensions for the
Bootstrap Protocol.
Note: We're not always able to receive unicast traffic before
being fully configured, e.g. with forward enabled. Then we need
to enable the broadcast flag under these situations.
endif

11
netutils/dhcpc/dhcpc.c
View File

@ -267,8 +267,12 @@ static int dhcpc_sendmsg(FAR struct dhcpc_state_s *pdhcpc,
/* Broadcast DISCOVER message to all servers */
case DHCPDISCOVER:
/* REVISIT: We don't need the broadcast flag since we can receive
* unicast traffic before being fully configured.
/* Socket binded to INADDR_ANY is not intended to receive unicast
* traffic before being fully configured, at least dhclient
* configured with socket-only won't do so on Linux and BSDs.
* We can sometimes receive unicast traffic before being fully
* configured, it's good, but not always, so we need to set the
* broadcast flag under some situations.
*/
/* Broadcast bit. */
@ -283,9 +287,6 @@ static int dhcpc_sendmsg(FAR struct dhcpc_state_s *pdhcpc,
/* Send REQUEST message to the server that sent the *first* OFFER */
case DHCPREQUEST:
/* REVISIT: We don't need the broadcast flag since we can receive
* unicast traffic before being fully configured.
*/
/* Broadcast bit. */