Merge patch series "BOOTP/DHCPv4 enhancements"
Sean Edmond <seanedmond@microsoft.com> says:
In our datacenter application, a single DHCP server is servicing 36000+ clients.
Improvements are required to the DHCPv4 retransmission behavior to align with
RFC and ensure less pressure is exerted on the server:
- retransmission backoff interval maximum is configurable
(environment variable bootpretransmitperiodmax)
- initial retransmission backoff interval is configurable
(environment variable bootpretransmitperiodinit)
- transaction ID is kept the same for each BOOTP/DHCPv4 request
(not recreated on each retry)
For our application we'll use:
- bootpretransmitperiodmax=16000
- bootpretransmitperiodinit=2000
A new configuration BOOTP_RANDOM_XID has been added to enable a randomized
BOOTP/DHCPv4 transaction ID.
Enhance DHCPv4 sending/parsing option 209 (PXE config file). A previous
patch was accepted. A new patch fixes a possible double free() and
addresses latest review comments.
Link: https://lore.kernel.org/r/20240509023918.2504185-1-seanedmond@microsoft.com
diff --git a/cmd/Kconfig b/cmd/Kconfig
index f21d27c..9a70c7a 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1986,6 +1986,7 @@
config BOOTP_PXE_DHCP_OPTION
bool "Request & store 'pxe_configfile' from BOOTP/DHCP server"
+ default y
depends on BOOTP_PXE
config BOOTP_VCI_STRING
@@ -1996,6 +1997,30 @@
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
+ hex
+ default 0x16 if ARM64
+ default 0x15 if ARM
+ default 0xFF
+
+config DHCP6_PXE_DHCP_OPTION
+ bool "Request & store 'pxe_configfile' from DHCP6 server"
+
+config DHCP6_ENTERPRISE_ID
+ int "Enterprise ID to send in DHCPv6 Vendor Class Option"
+ default 0
+
+endif
+
config CMD_TFTPPUT
bool "tftp put"
depends on CMD_TFTPBOOT
diff --git a/cmd/pxe.c b/cmd/pxe.c
index 0f26b3b..71d8b54 100644
--- a/cmd/pxe.c
+++ b/cmd/pxe.c
@@ -64,6 +64,8 @@
int ret = get_pxe_file(ctx, pxelinux_configfile, pxefile_addr_r);
free(pxelinux_configfile);
+ /* set to NULL to avoid double-free if DHCP is tried again */
+ pxelinux_configfile = NULL;
return ret;
}
diff --git a/lib/Kconfig b/lib/Kconfig
index cdf8f7e..6a89f79 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -283,7 +283,8 @@
choice
prompt "Pseudo-random library support type"
depends on NET_RANDOM_ETHADDR || RANDOM_UUID || CMD_UUID || \
- RNG_SANDBOX || UT_LIB && AES || FAT_WRITE
+ RNG_SANDBOX || UT_LIB && AES || FAT_WRITE || CMD_BOOTP || \
+ CMD_DHCP || CMD_DHCP6
default LIB_RAND
help
Select the library to provide pseudo-random number generator
diff --git a/net/bootp.c b/net/bootp.c
index afd5b48..f22921e 100644
--- a/net/bootp.c
+++ b/net/bootp.c
@@ -41,6 +41,22 @@
*/
#define TIMEOUT_MS ((3 + (CONFIG_NET_RETRY_COUNT * 5)) * 1000)
+/*
+ * According to rfc951 : 7.2. Client Retransmission Strategy
+ * "After the 'average' backoff reaches about 60 seconds, it should be
+ * increased no further, but still randomized."
+ *
+ * U-Boot has saturated this backoff at 2 seconds for a long time.
+ * To modify, set the environment variable "bootpretransmitperiodmax"
+ */
+#define RETRANSMIT_PERIOD_MAX_MS 60000
+
+/* Retransmission timeout for the initial packet (in milliseconds).
+ * This timeout will double on each retry. To modify, set the
+ * environment variable bootpretransmitperiodinit.
+ */
+#define RETRANSMIT_PERIOD_INIT_MS 250
+
#ifndef CFG_DHCP_MIN_EXT_LEN /* minimal length of extension list */
#define CFG_DHCP_MIN_EXT_LEN 64
#endif
@@ -52,6 +68,7 @@
u32 bootp_ids[CFG_BOOTP_ID_CACHE_SIZE];
unsigned int bootp_num_ids;
int bootp_try;
+u32 bootp_id;
ulong bootp_start;
ulong bootp_timeout;
char net_nis_domain[32] = {0,}; /* Our NIS domain */
@@ -59,6 +76,7 @@
char net_root_path[CONFIG_BOOTP_MAX_ROOT_PATH_LEN] = {0,}; /* Our bootpath */
static ulong time_taken_max;
+static u32 retransmit_period_max_ms;
#if defined(CONFIG_CMD_DHCP)
static dhcp_state_t dhcp_state = INIT;
@@ -395,6 +413,7 @@
static void bootp_timeout_handler(void)
{
ulong time_taken = get_timer(bootp_start);
+ int rand_minus_plus_100;
if (time_taken >= time_taken_max) {
#ifdef CONFIG_BOOTP_MAY_FAIL
@@ -413,8 +432,17 @@
}
} else {
bootp_timeout *= 2;
- if (bootp_timeout > 2000)
- bootp_timeout = 2000;
+ if (bootp_timeout > retransmit_period_max_ms)
+ bootp_timeout = retransmit_period_max_ms;
+
+ /* Randomize by adding bootp_timeout*RAND, where RAND
+ * is a randomization factor between -0.1..+0.1
+ */
+ srand(get_ticks() + rand());
+ rand_minus_plus_100 = ((rand() % 200) - 100);
+ bootp_timeout = bootp_timeout +
+ (((int)bootp_timeout * rand_minus_plus_100) / 1000);
+
net_set_timeout_handler(bootp_timeout, bootp_timeout_handler);
bootp_request();
}
@@ -602,7 +630,7 @@
*cnt += 1;
#endif
if (IS_ENABLED(CONFIG_BOOTP_PXE_DHCP_OPTION)) {
- *e++ = 209; /* PXELINUX Config File */
+ *e++ = DHCP_OPTION_PXE_CONFIG_FILE; /* PXELINUX Config File */
*cnt += 1;
}
/* no options, so back up to avoid sending an empty request list */
@@ -713,7 +741,8 @@
bootp_num_ids = 0;
bootp_try = 0;
bootp_start = get_timer(0);
- bootp_timeout = 250;
+
+ bootp_timeout = env_get_ulong("bootpretransmitperiodinit", 10, RETRANSMIT_PERIOD_INIT_MS);
}
void bootp_request(void)
@@ -725,7 +754,6 @@
#ifdef CONFIG_BOOTP_RANDOM_DELAY
ulong rand_ms;
#endif
- u32 bootp_id;
struct in_addr zero_ip;
struct in_addr bcast_ip;
char *ep; /* Environment pointer */
@@ -741,6 +769,9 @@
else
time_taken_max = TIMEOUT_MS;
+ retransmit_period_max_ms = env_get_ulong("bootpretransmitperiodmax", 10,
+ RETRANSMIT_PERIOD_MAX_MS);
+
#ifdef CONFIG_BOOTP_RANDOM_DELAY /* Random BOOTP delay */
if (bootp_try == 0)
srand_mac();
@@ -800,19 +831,27 @@
extlen = bootp_extended((u8 *)bp->bp_vend);
#endif
- /*
- * 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);
+ /* Only generate a new transaction ID for each new BOOTP request */
+ if (bootp_try == 1) {
+ 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
@@ -921,7 +960,7 @@
net_boot_file_name[size] = 0;
}
break;
- case 209: /* PXELINUX Config File */
+ case DHCP_OPTION_PXE_CONFIG_FILE: /* PXELINUX Config File */
if (IS_ENABLED(CONFIG_BOOTP_PXE_DHCP_OPTION)) {
/* In case it has already been allocated when get DHCP Offer packet,
* free first to avoid memory leak.
diff --git a/net/bootp.h b/net/bootp.h
index 521d38f..68320bf 100644
--- a/net/bootp.h
+++ b/net/bootp.h
@@ -90,6 +90,8 @@
#define DHCP_NAK 6
#define DHCP_RELEASE 7
+#define DHCP_OPTION_PXE_CONFIG_FILE 209 /* "ConfigFile" option according to rfc5071 */
+
/**********************************************************************/
#endif /* __BOOTP_H__ */