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>

include/net/net.h

@@ -56,8 +56,10 @@ typedef RxFilterInfo *(QueryRxFilter)(NetClientState *);
 typedef bool (HasUfo)(NetClientState *);
 typedef bool (HasVnetHdr)(NetClientState *);
 typedef bool (HasVnetHdrLen)(NetClientState *, int);
+typedef bool (GetUsingVnetHdr)(NetClientState *);
 typedef void (UsingVnetHdr)(NetClientState *, bool);
 typedef void (SetOffload)(NetClientState *, int, int, int, int, int);
+typedef int (GetVnetHdrLen)(NetClientState *);
 typedef void (SetVnetHdrLen)(NetClientState *, int);
 typedef int (SetVnetLE)(NetClientState *, bool);
 typedef int (SetVnetBE)(NetClientState *, bool);
@@ -84,8 +86,10 @@ typedef struct NetClientInfo {
     HasUfo *has_ufo;
     HasVnetHdr *has_vnet_hdr;
     HasVnetHdrLen *has_vnet_hdr_len;
+    GetUsingVnetHdr *get_using_vnet_hdr;
     UsingVnetHdr *using_vnet_hdr;
     SetOffload *set_offload;
+    GetVnetHdrLen *get_vnet_hdr_len;
     SetVnetHdrLen *set_vnet_hdr_len;
     SetVnetLE *set_vnet_le;
     SetVnetBE *set_vnet_be;
@@ -185,9 +189,11 @@ void qemu_format_nic_info_str(NetClientState *nc, uint8_t macaddr[6]);
 bool qemu_has_ufo(NetClientState *nc);
 bool qemu_has_vnet_hdr(NetClientState *nc);
 bool qemu_has_vnet_hdr_len(NetClientState *nc, int len);
+bool qemu_get_using_vnet_hdr(NetClientState *nc);
 void qemu_using_vnet_hdr(NetClientState *nc, bool enable);
 void qemu_set_offload(NetClientState *nc, int csum, int tso4, int tso6,
                       int ecn, int ufo);
+int qemu_get_vnet_hdr_len(NetClientState *nc);
 void qemu_set_vnet_hdr_len(NetClientState *nc, int len);
 int qemu_set_vnet_le(NetClientState *nc, bool is_le);
 int qemu_set_vnet_be(NetClientState *nc, bool is_be);

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;
 }
 

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) {

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,