Merge pull request #1795 from cagatay-y/mrgbuf-test

Test MRG_RXBUF

Author: mkroening

.github/workflows/ci.yml

@@ -249,6 +249,13 @@ jobs:
         working-directory: .
       - run: cargo xtask ci rs --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} --package httpd --features ci,hermit/dhcpv4,hermit/virtio-net qemu ${{ matrix.flags }} --devices virtio-net-pci
         if: matrix.arch != 'riscv64'
+      # FIXME: this is broken on QEMU 8.2.2
+      # Enable this once CI reaches QEMU 8.2.3 or QEMU 9.0.0 
+      # - run: cargo xtask ci rs --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} --package httpd --features ci,hermit/dhcpv4,hermit/virtio-net qemu ${{ matrix.flags }} --devices virtio-net-pci
+      #   if: matrix.arch != 'riscv64'
+      #   env:
+      #     # The buffer is sized to be smaller than the packets received during DHCPv4 address acquisition and thus exercise the buffer merging code path.
+      #     HERMIT_MRG_RXBUF_SIZE: 200
       - run: cargo xtask ci rs --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} --package httpd --features ci,hermit/virtio-net qemu --sudo --devices virtio-net-pci --tap
         if: matrix.arch != 'riscv64'
       - run: cargo xtask ci rs --arch ${{ matrix.arch }} --profile ${{ matrix.profile }} --package httpd --features ci,hermit/dhcpv4,hermit/virtio-net qemu ${{ matrix.flags }} --devices virtio-net-pci --no-default-virtio-features

src/drivers/net/virtio/mod.rs

@@ -13,6 +13,7 @@ cfg_if::cfg_if! {
 use alloc::boxed::Box;
 use alloc::vec::Vec;
 use core::mem::{ManuallyDrop, MaybeUninit, transmute};
+use core::str::FromStr;
 
 use smallvec::SmallVec;
 use smoltcp::phy::{Checksum, ChecksumCapabilities, DeviceCapabilities};
@@ -59,15 +60,24 @@ fn determine_mtu(dev_cfg: &NetDevCfg) -> u16 {
 	}
 }
 
-fn determine_buf_size(dev_cfg: &NetDevCfg) -> u32 {
+fn determine_rx_buf_size(dev_cfg: &NetDevCfg) -> u32 {
 	// See Virtio specification v1.1 - 5.1.6.3.1 and 5.1.4.2
 
 	// Our desired minimum buffer size - we want it to be at least the MTU generally
 	let mut min_buf_size = determine_mtu(dev_cfg).into();
 
 	// If VIRTIO_NET_F_MRG_RXBUF is negotiated, each buffer MUST be at least the size of the struct virtio_net_hdr.
 	// We just use MTU in that case, but otherwise...
-	if !dev_cfg.features.contains(virtio::net::F::MRG_RXBUF) {
+	if dev_cfg.features.contains(virtio::net::F::MRG_RXBUF)
+		&& let Some(my_mrg_rxbuf_size) = hermit_var!("HERMIT_MRG_RXBUF_SIZE")
+	{
+		let my_mrg_rxbuf_size = u32::from_str(&my_mrg_rxbuf_size).unwrap();
+		assert!(
+			my_mrg_rxbuf_size > 0,
+			"VIRTIO does not allow buffer elements of size 0."
+		);
+		min_buf_size = my_mrg_rxbuf_size;
+	} else {
 		// If [...] are negotiated, the driver SHOULD populate the receive queue(s) with buffers of at least 65562 bytes.
 		if dev_cfg.features.contains(virtio::net::F::GUEST_TSO4)
 			|| dev_cfg.features.contains(virtio::net::F::GUEST_TSO6)
@@ -92,7 +102,7 @@ impl RxQueues {
 	pub fn new(vqs: Vec<VirtQueue>, dev_cfg: &NetDevCfg) -> Self {
 		Self {
 			vqs,
-			buf_size: determine_buf_size(dev_cfg),
+			buf_size: determine_rx_buf_size(dev_cfg),
 		}
 	}
 
@@ -167,7 +177,7 @@ impl TxQueues {
 	pub fn new(vqs: Vec<VirtQueue>, dev_cfg: &NetDevCfg) -> Self {
 		Self {
 			vqs,
-			buf_size: determine_buf_size(dev_cfg),
+			buf_size: determine_mtu(dev_cfg).into(),
 		}
 	}