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.
Changes in v8: - remove unused variable "char *ep" from bootp_reset()
Changes in v7: - Remove "depends on LIB_RAND || LIB_HW_RAND" from CMD_BOOTP - Add CMD_BOOTP/CMD_DHCP/CMD_DHCP6 to LIB_RAND menu choice - Add space after "config CMD_DHCP"
Changes in v6: - CMD_BOOTP should "depends on LIB_RAND || LIB_HW_RAND"
Changes in v5: - add change log to individual patches - fix depends for BOOTP_RANDOM_XID: "depends on CMD_BOOTP && (LIB_RAND || LIB_HW_RAND)"
Changes in v4: - rebase master and resolve conflicts - default y for BOOTP_PXE_DHCP_OPTION (feedback from review) - Add "select LIB_RAND" for "config CMD_BOOTP" (retransmission improvements require rand())
Changes in v3: - add define for option 209 and rfc5071 reference - Set RETRANSMIT_PERIOD_MAX_MS=60000 - Add randomization factor to retransmission timeout - Add depends for BOOTP_RANDOM_XID
Changes in v2: - use env_get_ulong() to get environment variables
Sean Edmond (3): net: Enhancements for dhcp option 209 net: bootp: BOOTP/DHCPv4 retransmission improvements net: bootp: add config option BOOTP_RANDOM_XID
cmd/Kconfig | 8 ++++++ cmd/pxe.c | 2 ++ lib/Kconfig | 3 ++- net/bootp.c | 73 ++++++++++++++++++++++++++++++++++++++++------------- net/bootp.h | 2 ++ 5 files changed, 70 insertions(+), 18 deletions(-)