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>

3 files changed, 41 insertions, 4 deletions

diff --git a/net/dump.c b/net/dump.c
index 6a63b15359..7d05f16ca7 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;
 }
 
diff --git a/net/net.c b/net/net.c
index ebc7ce0231..6492ad530e 100644
--- a/net/net.c
+++ b/net/net.c
@@ -513,6 +513,15 @@ bool qemu_has_vnet_hdr_len(NetClientState *nc, int len)
     return nc->info->has_vnet_hdr_len(nc, len);
 }
 
+bool qemu_get_using_vnet_hdr(NetClientState *nc)
+{
+    if (!nc || !nc->info->get_using_vnet_hdr) {
+        return false;
+    }
+
+    return nc->info->get_using_vnet_hdr(nc);
+}
+
 void qemu_using_vnet_hdr(NetClientState *nc, bool enable)
 {
     if (!nc || !nc->info->using_vnet_hdr) {
@@ -532,6 +541,15 @@ void qemu_set_offload(NetClientState *nc, int csum, int tso4, int tso6,
     nc->info->set_offload(nc, csum, tso4, tso6, ecn, ufo);
 }
 
+int qemu_get_vnet_hdr_len(NetClientState *nc)
+{
+    if (!nc || !nc->info->get_vnet_hdr_len) {
+        return 0;
+    }
+
+    return nc->info->get_vnet_hdr_len(nc);
+}
+
 void qemu_set_vnet_hdr_len(NetClientState *nc, int len)
 {
     if (!nc || !nc->info->set_vnet_hdr_len) {
diff --git a/net/tap.c b/net/tap.c
index 7d7bc1dc5f..1bf085d422 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -255,6 +255,13 @@ static bool tap_has_vnet_hdr_len(NetClientState *nc, int len)
     return !!tap_probe_vnet_hdr_len(s->fd, len);
 }
 
+static int tap_get_vnet_hdr_len(NetClientState *nc)
+{
+    TAPState *s = DO_UPCAST(TAPState, nc, nc);
+
+    return s->host_vnet_hdr_len;
+}
+
 static void tap_set_vnet_hdr_len(NetClientState *nc, int len)
 {
     TAPState *s = DO_UPCAST(TAPState, nc, nc);
@@ -268,6 +275,13 @@ static void tap_set_vnet_hdr_len(NetClientState *nc, int len)
     s->host_vnet_hdr_len = len;
 }
 
+static bool tap_get_using_vnet_hdr(NetClientState *nc)
+{
+    TAPState *s = DO_UPCAST(TAPState, nc, nc);
+
+    return s->using_vnet_hdr;
+}
+
 static void tap_using_vnet_hdr(NetClientState *nc, bool using_vnet_hdr)
 {
     TAPState *s = DO_UPCAST(TAPState, nc, nc);
@@ -372,8 +386,10 @@ static NetClientInfo net_tap_info = {
     .has_ufo = tap_has_ufo,
     .has_vnet_hdr = tap_has_vnet_hdr,
     .has_vnet_hdr_len = tap_has_vnet_hdr_len,
+    .get_using_vnet_hdr = tap_get_using_vnet_hdr,
     .using_vnet_hdr = tap_using_vnet_hdr,
     .set_offload = tap_set_offload,
+    .get_vnet_hdr_len = tap_get_vnet_hdr_len,
     .set_vnet_hdr_len = tap_set_vnet_hdr_len,
     .set_vnet_le = tap_set_vnet_le,
     .set_vnet_be = tap_set_vnet_be,