net: remove loopback XDP socket

Removes the loopback XDP socket from the net tile.  Also removes
the ethtool-loopback configure stage.  Loopback is done via a sock
tile in the future.

Author: riptl

book/api/cli.md

@@ -70,7 +70,6 @@ following stages to each configure command:
     device.
  - `ethtool-gro` Disables generic receive offload (GRO) on the network
     device.
- - `ethtool-loopback` Disables UDP segmentation on the loopback device.
 
 | Arguments         | Description |
 |-------------------|-------------|
@@ -102,7 +101,6 @@ and configure the number of combined channels on the network device.
 | `root`          | increase `/proc/sys/vm/nr_hugepages` and mount hugetlbfs filesystems. Only applies for the `hugetlbfs` stage |
 | `root`          | increase network device channels with `ethtool --set-channels`. Only applies for the `ethtool-channels` stage |
 | `root`          | disable network device generic-receive-offload (gro) with `ethtool --offload IFACE generic-receive-offload off`. Only applies for the `ethtool-gro` stage |
-| `root`          | disable network device tx-udp-segmentation with `ethtool --offload lo tx-udp-segmentation off`. Only applies for the `ethtool-loopback` stage |
 | `CAP_SYS_ADMIN` | set kernel parameters in `/proc/sys`. Only applies for the `sysctl` stage |
 
 :::

book/guide/initializing.md

@@ -11,8 +11,6 @@ so Firedancer can run correctly. It does the following:
 device.
 * **ethtool-gro** Disable generic-receive-offload (GRO) on the network
 device.
-* **ethtool-loopback** Disable tx-udp-segmentation on the loopback
-device.
 
 The `hugetlbfs` configuration must be performed every time the system
 is rebooted, to remount the `hugetlbfs` filesystems, as do `sysctl`,
@@ -30,7 +28,7 @@ where `mode` is one of:
  - `fini` Unconfigure (reverse) the stage if it is reversible.
 
 `stage` can be one or more of `hugetlbfs`, `sysctl`, `hyperthreads`,
-`ethtool-channels`, `ethtool-gro`, `ethtool-loopback`, and `snapshots`
+`ethtool-channels`, `ethtool-gro`, and `snapshots`
 and these stages are described below. You can also use the stage `all`
 which will configure everything.
 
@@ -193,22 +191,6 @@ Firedancer. It has no dependencies on any other stage.
 Changing device settings with `ethtool-gro` requires root privileges, and
 cannot be performed with capabilities.
 
-## ethtool-loopback
-XDP is incompatible with localhost UDP traffic using a feature called
-`tx-udp-segmentation`. This feature must be disabled when connecting Agave
-clients to Firedancer over loopback, or when using Frankendancer.
-
-The command run by the stage is `ethtool --offload lo tx-udp-segmentation
-off`. We can check that it worked:
-
-<<< @/snippets/ethtool-loopback.ansi
-
-The stage only needs to be run once after boot but before running
-Firedancer. It has no dependencies on any other stage.
-
-Changing device settings with `ethtool-loopback` requires root privileges,
-and cannot be performed with capabilities.
-
 ## snapshots
 When starting up, validators must load a snapshot to catch up to the
 current state of the blockchain. Snapshots are downloaded from other

book/guide/internals/net_tile.md

@@ -426,28 +426,6 @@ completion ring.
 
 The net tile moves completed frames back to the free ring.
 
-## Loopback
-
-The first net tile (`net:0`) sets up XDP on the loopback device, for
-two main reasons:
-
-* For testing and development.
-* The Agave code sends local traffic to itself to as part of routine
-  operation (e.g., when it's the leader it sends votes to its own TPU
-  socket).
-
-The Linux kernel routes outgoing packets addressed to IP addresses
-owned by the system via loopback.  (See `ip route show table local`)
-The net tile partially matches this behavior.  For better performance
-and simplicity, a second XDP socket is used.
-
-Alternatively, the net tile could have sent such traffic out to the
-public gateway, in hopes that the traffic gets mirrored back.
-
-But for now, Firedancer also binds XDP to loopback. This is a small performance hit for other traffic, but otherwise won't interfere.
-
-The loopback device only supports XDP in SKB mode.
-
 ## Development
 
 ### Network Namespace

book/snippets/commands/configure-check.ansi

@@ -3,5 +3,4 @@ $ fdctl configure check all
 WARNING sysctl ... not configured ... kernel parameter `/proc/sys/vm/max_map_count` is too low (got 65536 but expected at least 1000000)
 WARNING ethtool-channels ... not configured ... device `ens3f0` does not have right number of channels (got 1 but expected 2)
 WARNING ethtool-gro ... not configured ... device `ens3f0` has generic-receive-offload enabled. Should be disabled
-WARNING ethtool-loopback ... not configured ... device `lo` has tx-udp-segmentation enabled. Should be disabled
 ERR     failed to configure some stages

book/snippets/commands/configure-init.ansi

@@ -23,6 +23,3 @@ $ fdctl configure init all
 NOTICE  ethtool-gro ... unconfigured ... device `ens3f0` has generic-receive-offload enabled. Should be disabled
 NOTICE  ethtool-gro ... configuring
 NOTICE  ethtool-gro ... RUN: `ethtool --offload ens3f0 generic-receive-offload off`
-NOTICE  ethtool-loopback ... unconfigured ... device `lo` has tx-udp-segmentation enabled. Should be disabled
-NOTICE  ethtool-loopback ... configuring
-NOTICE  ethtool-loopback ... RUN: `ethtool --offload lo tx-udp-segmentation off`

book/snippets/configure.ansi

@@ -7,4 +7,3 @@
 NOTICE  sysctl ... already valid
 NOTICE  ethtool-channels ... already valid
 NOTICE  ethtool-gro ... already valid
-NOTICE  ethtool-loopback ... already valid

book/snippets/ethtool-loopback.ansi

@@ -85,7 +85,6 @@ echo "
 sudo $FD_DIR/$OBJDIR/bin/firedancer-dev configure init kill --config $(readlink -f firedancer-dev.toml)
 sudo $FD_DIR/$OBJDIR/bin/firedancer-dev configure init hugetlbfs --config $(readlink -f firedancer-dev.toml)
 sudo $FD_DIR/$OBJDIR/bin/firedancer-dev configure init ethtool-channels --config $(readlink -f firedancer-dev.toml)
-sudo $FD_DIR/$OBJDIR/bin/firedancer-dev configure init ethtool-gro ethtool-loopback --config $(readlink -f firedancer-dev.toml)
 sudo $FD_DIR/$OBJDIR/bin/firedancer-dev configure init keys --config $(readlink -f firedancer-dev.toml)
 
 sudo gdb -iex="set debuginfod enabled on" -ex=r --args $FD_DIR/$OBJDIR/bin/firedancer-dev dev --no-configure --log-path $(readlink -f firedancer-dev.log) --config $(readlink -f firedancer-dev.toml)

contrib/test/test_firedancer_leader.sh

@@ -38,7 +38,6 @@ configure_stage_t * STAGES[] = {
   &fd_cfg_stage_hyperthreads,
   &fd_cfg_stage_ethtool_channels,
   &fd_cfg_stage_ethtool_gro,
-  &fd_cfg_stage_ethtool_loopback,
   NULL,
 };
 

src/app/fdctl/main.c

@@ -48,7 +48,6 @@ configure_stage_t * STAGES[] = {
   &fd_cfg_stage_hyperthreads,
   &fd_cfg_stage_ethtool_channels,
   &fd_cfg_stage_ethtool_gro,
-  &fd_cfg_stage_ethtool_loopback,
   &fd_cfg_stage_keys,
   &fd_cfg_stage_genesis,
   &fd_cfg_stage_blockstore,