[PATCH v6 3/3] net: bootp: add config option BOOTP_RANDOM_XID

Sean Edmond
2023-11-22T23:34:40Z

The new config option BOOTP_RANDOM_XID will randomize the transaction ID
for each new BOOT/DHCPv4 exchange.

Signed-off-by: Sean Edmond <seanedmond@microsoft.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

---

(no changes since v5)

Changes in v5:
- fix depends for BOOTP_RANDOM_XID:
"depends on CMD_BOOTP && (LIB_RAND || LIB_HW_RAND)"

Changes in v3:
- Add depends for BOOTP_RANDOM_XID

cmd/Kconfig | 7 +++++++
net/bootp.c | 31 +++++++++++++++++--------------
2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/cmd/Kconfig b/cmd/Kconfig
index 6b7c5e6d521..8204f72f6ac 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1853,6 +1853,13 @@ config BOOTP_VCI_STRING
default "U-Boot.arm" if ARM
default "U-Boot"

+config BOOTP_RANDOM_XID
+ bool "Send random transaction ID to BOOTP/DHCP server"
+ depends on CMD_BOOTP && (LIB_RAND || LIB_HW_RAND)
+ help
+ Selecting this will allow for a random transaction ID to get
+ selected for each BOOTP/DHCPv4 exchange.
+
if CMD_DHCP6

config DHCP6_PXE_CLIENTARCH
diff --git a/net/bootp.c b/net/bootp.c
index 89425717328..49cd9064436 100644
--- a/net/bootp.c
+++ b/net/bootp.c
@@ -837,22 +837,25 @@ void bootp_request(void)

/* Only generate a new transaction ID for each new BOOTP request */
if (bootp_try == 1) {
- /*
- * Bootp ID is the lower 4 bytes of our ethernet address
- * plus the current time in ms.
- */
- bootp_id = ((u32)net_ethaddr[2] << 24)
- | ((u32)net_ethaddr[3] << 16)
- | ((u32)net_ethaddr[4] << 8)
- | (u32)net_ethaddr[5];
- bootp_id += get_timer(0);
- bootp_id = htonl(bootp_id);
- bootp_add_id(bootp_id);
- net_copy_u32(&bp->bp_id, &bootp_id);
- } else {
- net_copy_u32(&bp->bp_id, &bootp_id);
+ if (IS_ENABLED(CONFIG_BOOTP_RANDOM_XID)) {
+ srand(get_ticks() + rand());
+ bootp_id = rand();
+ } else {
+ /*
+ * Bootp ID is the lower 4 bytes of our ethernet address
+ * plus the current time in ms.
+ */
+ bootp_id = ((u32)net_ethaddr[2] << 24)
+ | ((u32)net_ethaddr[3] << 16)
+ | ((u32)net_ethaddr[4] << 8)
+ | (u32)net_ethaddr[5];
+ bootp_id += get_timer(0);
+ bootp_id = htonl(bootp_id);
+ }
}

+ bootp_add_id(bootp_id);
+ net_copy_u32(&bp->bp_id, &bootp_id);
/*
* Calculate proper packet lengths taking into account the
* variable size of the options field
--
2.42.0