chore: Update naming of VsockError variants

Some of the variants still explicitly reflected the "two descriptors per
packet" assumptions. Change naming here to instead refer to the length
of the entire descriptor chain. Also include some more information about
what the actual lengths and expections are.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

src/vmm/src/devices/virtio/vsock/mod.rs

@@ -107,9 +107,10 @@ mod defs {
 
 /// Vsock device related errors.
 #[derive(Debug, thiserror::Error, displaydoc::Display)]
+#[rustfmt::skip]
 pub enum VsockError {
-    /// The vsock data/buffer virtio descriptor length is smaller than expected.
-    BufDescTooSmall,
+    /** The total length of the descriptor chain ({0}) is too short to hold a packet of length {1} + header */
+    DescChainTooShortForPacket(usize, u32),
     /// Empty queue
     EmptyQueue,
     /// EventFd error: {0}
@@ -118,8 +119,9 @@ pub enum VsockError {
     GuestMemoryMmap(GuestMemoryError),
     /// Bounds check failed on guest memory pointer.
     GuestMemoryBounds,
-    /// The vsock header descriptor length is too small: {0}
-    HdrDescTooSmall(usize),
+    /** The total length of the descriptor chain ({0}) is less than the number of bytes required\
+    to hold a vsock packet header.*/
+    DescChainTooShortForHeader(usize),
     /// The vsock header `len` field holds an invalid value: {0}
     InvalidPktLen(u32),
     /// A data fetch was attempted when no data was available.

src/vmm/src/devices/virtio/vsock/packet.rs

@@ -116,27 +116,30 @@ impl VsockPacket {
     /// Returns
     /// - [`VsockError::UnreadableDescriptor`] if the provided descriptor chain contains any
     ///   descriptor not marked as writable.
-    /// - [`VsockError::HdrDescTooSmall`] if the descriptor chain's total buffer length is
-    ///   insufficient to hold the 44 byte vsock header
+    /// - [`VsockError::DescChainTooShortForHeader`] if the descriptor chain's total buffer length
+    ///   is insufficient to hold the 44 byte vsock header
     /// - [`VsockError::InvalidPktLen`] if the contained vsock header describes a vsock packet whose
     ///   length would exceed [`defs::MAX_PKT_BUR_SIZE`].
-    /// - [`VsockError::BufDescTooSmall`] if the contained vsock header describes a vsock packet
-    ///   whose length exceeds the descriptor chain's actual total buffer length.
+    /// - [`VsockError::DescChainTooShortForPacket`] if the contained vsock header describes a vsock
+    ///   packet whose length exceeds the descriptor chain's actual total buffer length.
     pub fn from_tx_virtq_head(chain: DescriptorChain) -> Result<Self, VsockError> {
         let buffer = IoVecBuffer::from_descriptor_chain(chain)?;
 
         let mut hdr = VsockPacketHeader::default();
         let header_bytes_read = buffer.read_at(hdr.as_mut_slice(), 0).unwrap_or(0);
         if header_bytes_read < VSOCK_PKT_HDR_SIZE as usize {
-            return Err(VsockError::HdrDescTooSmall(header_bytes_read));
+            return Err(VsockError::DescChainTooShortForHeader(header_bytes_read));
         }
 
         if hdr.len > defs::MAX_PKT_BUF_SIZE {
             return Err(VsockError::InvalidPktLen(hdr.len));
         }
 
         if (hdr.len as usize) > buffer.len() - VSOCK_PKT_HDR_SIZE as usize {
-            return Err(VsockError::BufDescTooSmall);
+            return Err(VsockError::DescChainTooShortForPacket(
+                buffer.len(),
+                hdr.len,
+            ));
         }
 
         Ok(VsockPacket {
@@ -148,13 +151,13 @@ impl VsockPacket {
     /// Create the packet wrapper from an RX virtq chain head.
     ///
     /// ## Errors
-    /// Returns [`VsockError::HdrDescTooSmall`] if the descriptor chain's total buffer length is
-    /// insufficient to hold the 44 byte vsock header
+    /// Returns [`VsockError::DescChainTooShortForHeader`] if the descriptor chain's total buffer
+    /// length is insufficient to hold the 44 byte vsock header
     pub fn from_rx_virtq_head(chain: DescriptorChain) -> Result<Self, VsockError> {
         let buffer = IoVecBufferMut::from_descriptor_chain(chain)?;
 
         if buffer.len() < VSOCK_PKT_HDR_SIZE as usize {
-            return Err(VsockError::HdrDescTooSmall(buffer.len()));
+            return Err(VsockError::DescChainTooShortForHeader(buffer.len()));
         }
 
         Ok(Self {
@@ -444,7 +447,12 @@ mod tests {
                 .len
                 .set(VSOCK_PKT_HDR_SIZE - 1);
             handler_ctx.guest_txvq.dtable[1].len.set(0);
-            expect_asm_error!(tx, test_ctx, handler_ctx, VsockError::HdrDescTooSmall(_));
+            expect_asm_error!(
+                tx,
+                test_ctx,
+                handler_ctx,
+                VsockError::DescChainTooShortForHeader(_)
+            );
         }
 
         // Test case: zero-length TX packet.
@@ -477,7 +485,12 @@ mod tests {
             create_context!(test_ctx, handler_ctx);
             set_pkt_len(1024, &handler_ctx.guest_txvq.dtable[0], &test_ctx.mem);
             handler_ctx.guest_txvq.dtable[0].flags.set(0);
-            expect_asm_error!(tx, test_ctx, handler_ctx, VsockError::BufDescTooSmall);
+            expect_asm_error!(
+                tx,
+                test_ctx,
+                handler_ctx,
+                VsockError::DescChainTooShortForPacket(44, 1024)
+            );
         }
 
         // Test case: error on write-only buf descriptor.
@@ -495,7 +508,12 @@ mod tests {
             create_context!(test_ctx, handler_ctx);
             set_pkt_len(8 * 1024, &handler_ctx.guest_txvq.dtable[0], &test_ctx.mem);
             handler_ctx.guest_txvq.dtable[1].len.set(4 * 1024);
-            expect_asm_error!(tx, test_ctx, handler_ctx, VsockError::BufDescTooSmall);
+            expect_asm_error!(
+                tx,
+                test_ctx,
+                handler_ctx,
+                VsockError::DescChainTooShortForPacket(4140, 8192)
+            );
         }
     }
 
@@ -530,7 +548,12 @@ mod tests {
                 .len
                 .set(VSOCK_PKT_HDR_SIZE - 1);
             handler_ctx.guest_rxvq.dtable[1].len.set(0);
-            expect_asm_error!(rx, test_ctx, handler_ctx, VsockError::HdrDescTooSmall(_));
+            expect_asm_error!(
+                rx,
+                test_ctx,
+                handler_ctx,
+                VsockError::DescChainTooShortForHeader(_)
+            );
         }
     }