Re: [PATCH 1/7] tap: Move the tap_hdr file to a separate file

9 Sep 2026

On Wed, Sep 09, 2026 at 10:47:25AM +0200, Laurent Vivier wrote:
...
Subject: s/tap_hdr file/tap_hdr structure/
On 9/4/26 23:28, aerosouund wrote:
...
From: Ammar Yasser 
It was defined in tap.h, put it on its own so that future callers won't
need to depend on all definitions in tap.h.
Also turn it into a union of a vnet_len and virtio_net_mrg_rxbuf
because for vhost acceleration the frames will have this virtio net
header prepended to them.
Signed-off-by: Eugenio Pérez 
If Eugenio is the author, you should set it as the author, otherwise you
should remove his Signed-off-by
I don't think that's necessarily correct.  If the patch has been
changed substantially enough from the original, it makes sense to
change the author.  However, the S-o-b should remain if some fragments
of the original remain, so as to still record the chain of hands
through which it has passed for the DCO.
...
...
Signed-off-by: Ammar Yasser 
---
  tap.h     |  9 +--------
  tap_hdr.h | 23 +++++++++++++++++++++++
  2 files changed, 24 insertions(+), 8 deletions(-)
  create mode 100644 tap_hdr.h

diff --git a/tap.h b/tap.h
index b335933..1625975 100644
--- a/tap.h
+++ b/tap.h
@@ -10,6 +10,7 @@
  #include 
  #include "passt.h"
+#include "tap_hdr.h"
  /** L2_MAX_LEN_PASTA - Maximum frame length for pasta mode (with L2 header)
   *
@@ -38,14 +39,6 @@
  struct udphdr;
-/**
- * struct tap_hdr - tap backend specific headers
- * @vnet_len:	Frame length (for qemu socket transport)
- */
-struct tap_hdr {
-	uint32_t vnet_len;
-} __attribute__((packed));
-
  /**
   * tap_hdr_iov() - struct iovec for a tap header
   * @c:		Execution context
diff --git a/tap_hdr.h b/tap_hdr.h
new file mode 100644
index 0000000..aa270b7
--- /dev/null
+++ b/tap_hdr.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (c) 2021 Red Hat GmbH
+ * Author: Stefano Brivio 
+ */
+
+#ifndef TAP_HDR_H
+#define TAP_HDR_H
+
+#include 
+#include 
+
+/**
+ * struct tap_hdr - tap backend specific headers
+ * @vnet_len:	Frame length (for qemu socket transport)
missing @hdr description
...
+ */
+struct tap_hdr {
+	union {
+		uint32_t vnet_len;
+		struct virtio_net_hdr_mrg_rxbuf hdr;
+	};
+};
This will break passt.
In tap.h, we have:
static inline struct iovec tap_hdr_iov(const struct ctx *c,
                                       struct tap_hdr *thdr)
{
        return (struct iovec){
                .iov_base = thdr,
                .iov_len = c->mode == MODE_PASST ? sizeof(*thdr) : 0,
        };
}
before this patch sizeof(*thdr) is 4, now it's 12.
...
+
+#endif /* TAP_HDR_H */
-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

    