net: Strip virtio-net header when dumping

filter-dump specifiees Ethernet as PCAP LinkType, which does not expect
virtio-net header. Having virtio-net header in such PCAP file breaks
PCAP unconsumable. Unfortunately currently there is no LinkType for
virtio-net so for now strip virtio-net header to convert the output to
Ethernet.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/net/dump.c b/net/dump.c
index 6a63b15..7d05f16 100644
--- a/net/dump.c
+++ b/net/dump.c
@@ -61,12 +61,13 @@ struct pcap_sf_pkthdr {
     uint32_t len;
 };
 
-static ssize_t dump_receive_iov(DumpState *s, const struct iovec *iov, int cnt)
+static ssize_t dump_receive_iov(DumpState *s, const struct iovec *iov, int cnt,
+                                int offset)
 {
     struct pcap_sf_pkthdr hdr;
     int64_t ts;
     int caplen;
-    size_t size = iov_size(iov, cnt);
+    size_t size = iov_size(iov, cnt) - offset;
     struct iovec dumpiov[cnt + 1];
 
     /* Early return in case of previous error. */
@@ -84,7 +85,7 @@ static ssize_t dump_receive_iov(DumpState *s, const struct iovec *iov, int cnt)
 
     dumpiov[0].iov_base = &hdr;
     dumpiov[0].iov_len = sizeof(hdr);
-    cnt = iov_copy(&dumpiov[1], cnt, iov, cnt, 0, caplen);
+    cnt = iov_copy(&dumpiov[1], cnt, iov, cnt, offset, caplen);
 
     if (writev(s->fd, dumpiov, cnt + 1) != sizeof(hdr) + caplen) {
         error_report("network dump write error - stopping dump");
@@ -153,8 +154,10 @@ static ssize_t filter_dump_receive_iov(NetFilterState *nf, NetClientState *sndr,
                                        int iovcnt, NetPacketSent *sent_cb)
 {
     NetFilterDumpState *nfds = FILTER_DUMP(nf);
+    int offset = qemu_get_using_vnet_hdr(nf->netdev) ?
+                 qemu_get_vnet_hdr_len(nf->netdev) : 0;
 
-    dump_receive_iov(&nfds->ds, iov, iovcnt);
+    dump_receive_iov(&nfds->ds, iov, iovcnt, offset);
     return 0;
 }