GRUB's TCP stack assigns source ports for outgoing connections starting
at 21550 and increments sequentially by 1 (e.g., 21550, 21551, ...).
While this generally works, it can lead to failures if the system
reboots rapidly and reuses the same source port too soon.
This issue was observed on powerpc-ieee1275 platforms using CAS (Client
Architecture Support) reboot. In such cases, loading the initrd over
HTTP may fail with connection timeouts. Packet captures show the failed
connections are flagged as "TCP Port Number Reused" by Wireshark.
The root cause is that GRUB reuses the same port shortly after reboot,
while the server may still be tracking the previous connection in
TIME_WAIT. This can result in the server rejecting the connection
attempt or responding with a stale ACK or RST, leading to handshake
failure.
This patch fixes the issue by introducing a time based source port
selection strategy. Instead of always starting from port 21550, GRUB now
computes an initial base port based on the current RTC time, divided
into 5 minute windows. The purpose of this time based strategy is to
ensure that GRUB avoids reusing the same source port within a 5 minute
window, thereby preventing collisions with stale server side connection
tracking that could interfere with a new TCP handshake.
A step size of 8 ensures that the same port will not be reused across
reboots unless GRUB opens more than 8 TCP connections per second on
average, something that is highly unlikely. In typical usage, a GRUB
boot cycle lasts about 15 seconds and may open fewer than 100
connections total, well below the reuse threshold. This makes the
approach robust against short reboot intervals while keeping the logic
simple and deterministic.
Signed-off-by: Michael Chang <mchang@suse.com>
Reviewed-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
If the machine has network cards found, but there are no tcp open sockets
(because the user doesn't use the network to boot), then grub_net_tcp_retransmit()
should be a noop. Thus GRUB doesn't need to call grub_get_time_ms(), which
does a call into firmware on powerpc-ieee1275, and probably other targets.
So only call grub_get_time_ms() if there are tcp sockets.
Aside from improving performance, its also useful to stay out of the firmware
as much as possible when debugging via QEMU because its a pain to get back
in to GRUB execution. grub_net_tcp_retransmit() can get called very frequently
via grub_net_poll_cards_idle() when GRUB is waiting for a keypress
(grub_getkey_noblock() calls grub_net_poll_cards_idle()). This can be annoying
when debugging an issue in GRUB on PowerPC in QEMU with GDB when GRUB is waiting
for a keypress because interrupting via GDB nearly always lands in the OpenBIOS
firmware's milliseconds call.
Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
While adding tcp window scaling support I was finding that I'd get some packet
loss or reordering when transferring from large distances and grub would just
timeout. This is because we weren't ack'ing when we got our OOO packet, so the
sender didn't know it needed to retransmit anything, so eventually it would fill
the window and stop transmitting, and we'd time out. Fix this by ACK'ing when
we don't find our next sequence numbered packet. With this fix I no longer time
out. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Using the http module to download config files, produces memory errors,
after the config file is downloaded.
The error was traced to the tcp stack in grub-core/net/tcp.c. The wrong
netbuff pointer was being freed in the clean up loop.
Changing the code to free the correct netbuff pointer removes the runtime
error.
Closes 42765.
* grub-core/net/http.c (parse_line): Handle response 206.
(http_receive): Stall if too many packets are in the queue.
(http_establish): Fix range header.
(http_seek): Fix double free.
(http_close): Likewise.
(http_packets_pulled): New function.
(grub_http_protocol): Set http_seek
* grub-core/net/tcp.c (grub_net_tcp_socket): New field `i_stall'.
(ack_real): Set window depending on i_stall.
(grub_net_send_tcp_packet): Likewise.
(grub_net_tcp_stall): New function.
(grub_net_tcp_unstall): Likewise.
* include/grub/net/tcp.h (grub_net_tcp_stall): New proto.
(grub_net_tcp_unstall): Likewise.
* include/grub/net.h (grub_net_poll_cards): New argument stop_condition.
All users updated.
* grub-core/net/arp.c (have_pending): New var.
(pending_req): Likewise.
(grub_net_arp_send_request): Fill pending_req and use have_pending as
stop indicator.
(grub_net_arp_receive): Set have_pending.
* grub-core/net/dns.c (recv_data): New field stop.
(recv_hook): Set stop.
(grub_net_dns_lookup): Init stop and use as stop condition.
* grub-core/net/http.c (http_establish): Use headers_recv as stop
condition.
* grub-core/net/net.c (grub_net_poll_cards): New argument
stop_condition. Stop when it goes true.
* grub-core/net/tcp.c (grub_net_tcp_open): Use `established' as stop
indicator.
* grub-core/net/tftp.c (tftp_open): Use `have_oack' as stop indicator.
compact and more efficient code.
* grub-core/kern/list.c (grub_list_push): Moved from here ...
* include/grub/list.h (grub_list_push): ... to here. Set prev.
(grub_list_remove): Moved from here ...
* include/grub/list.h (grub_list_remove): ... here. Use and set prev.
(grub_prio_list_insert): Set prev.
* include/grub/list.h (grub_list): Add prev. All users updated.
