Move the segment check up

Author: sunilmut

vm/devices/net/net_mana/src/lib.rs

@@ -1300,6 +1300,22 @@ impl<T: DeviceBacking> ManaQueue<T> {
 
             let mut segment_count =
                 tail_sgl_offset + meta.segment_count as usize - header_segment_count;
+
+            // Drop the LSO packet if it only has a header segment.
+            // In production builds, this check always runs.
+            // For tests, use test hooks to bypass this check for allowing code coverage.
+            #[cfg(not(test))]
+            let check_lso_segment_count = true;
+            #[cfg(test)]
+            let check_lso_segment_count = !self.test_configuration.allow_lso_pkt_with_one_sge;
+
+            if check_lso_segment_count
+                && meta.flags.offload_tcp_segmentation()
+                && segment_count == 1
+            {
+                return Ok(None);
+            }
+
             let mut sgl_idx = tail_sgl_offset - 1;
             let sgl = if segment_count <= hardware_segment_limit {
                 for (tail, sge) in segments[header_segment_count..]