net: Add a new libpcap-based client

net/clients.h

@@ -63,4 +63,8 @@ int net_init_vhost_user(const Netdev *netdev, const char *name,
 
 int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
                         NetClientState *peer, Error **errp);
+
+int net_init_pcap(const Netdev *netdev, const char *name,
+                  NetClientState *peer, Error **errp);
+
 #endif /* QEMU_NET_CLIENTS_H */

net/meson.build

@@ -37,5 +37,6 @@ endif
 softmmu_ss.add(when: 'CONFIG_POSIX', if_true: files(tap_posix))
 softmmu_ss.add(when: 'CONFIG_WIN32', if_true: files('tap-win32.c'))
 softmmu_ss.add(when: 'CONFIG_VHOST_NET_VDPA', if_true: files('vhost-vdpa.c'))
+softmmu_ss.add([libpcap, files('pcap.c')])
 
 subdir('can')

net/net.c

@@ -1002,6 +1002,7 @@ static int (* const net_client_init_fun[NET_CLIENT_DRIVER__MAX])(
 #ifdef CONFIG_L2TPV3
         [NET_CLIENT_DRIVER_L2TPV3]    = net_init_l2tpv3,
 #endif
+        [NET_CLIENT_DRIVER_PCAP]      = net_init_pcap,
 };
 
 

net/pcap.c

@@ -0,0 +1,178 @@
+/*
+ * QEMU libpcap network client
+ *
+ * Copyright (C) 2021 Matt Borgerson
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "net/net.h"
+#include "net/eth.h"
+#include "net/clients.h"
+#include "clients.h"
+#include "sysemu/sysemu.h"
+#include "qemu/error-report.h"
+#include "qapi/error.h"
+#include "qemu/iov.h"
+#include "qemu/cutils.h"
+#include "qemu/main-loop.h"
+#include "net/pcap.h"
+
+#if 0
+#define LOG(fmt, ...) fprintf(stderr, "%s: " fmt "\n", __func__, ##__VA_ARGS__)
+#else
+#define LOG(...) do {} while (0)
+#endif
+
+typedef struct NetPcapState {
+    NetClientState nc;
+    char *ifname;
+    pcap_t *p;
+#ifdef WIN32
+    HANDLE fd;
+#else
+    int fd;
+    bool read_poll;
+#endif
+} NetPcapState;
+
+static ssize_t net_pcap_receive(NetClientState *nc, const uint8_t *buf,
+                                size_t size)
+{
+    NetPcapState *s = DO_UPCAST(NetPcapState, nc, nc);
+    LOG("qemu->pcap %zd bytes...", size);
+
+    if (pcap_sendpacket(s->p, buf, size)) {
+        LOG("pcap_sendpacket failed!\n");
+        return -1;
+    }
+
+    return size;
+}
+
+static void net_pcap_cleanup(NetClientState *nc)
+{
+    NetPcapState *s = DO_UPCAST(NetPcapState, nc, nc);
+#if defined(_WIN32)
+    qemu_del_wait_object(s->fd, NULL, NULL);
+#endif
+    pcap_close(s->p);
+    free(s->ifname);
+}
+
+static NetClientInfo net_pcap_info = {
+    .type = NET_CLIENT_DRIVER_PCAP,
+    .size = sizeof(NetPcapState),
+    .receive = net_pcap_receive,
+    .cleanup = net_pcap_cleanup,
+};
+
+static void net_pcap_send(void *opaque)
+{
+    NetPcapState *s = opaque;
+    struct pcap_pkthdr *pkt_header;
+    const u_char *buf;
+    uint8_t min_pkt[ETH_ZLEN];
+    size_t min_pktsz = sizeof(min_pkt);
+
+    int status = pcap_next_ex(s->p, &pkt_header, &buf);
+    if (status == 1) {
+        /* Success */
+    } else if (status == 0) {
+        /* Timeout */
+        return;
+    } else if (status == -1) {
+        LOG("pcap_next_ex error: %s", pcap_geterr(s->p));
+        return;
+    } else {
+        LOG("unknown pcap error %d\n", status);
+        return;
+    }
+
+    size_t size = pkt_header->len;
+    assert(size >= 14);
+    assert(pkt_header->caplen == size);
+
+    if (size > 0) {
+        if (net_peer_needs_padding(&s->nc)) {
+            if (eth_pad_short_frame(min_pkt, &min_pktsz, buf, size)) {
+                buf = min_pkt;
+                size = min_pktsz;
+            }
+        }
+
+        LOG("pcap->qemu %zd bytes", size);
+        qemu_send_packet(&s->nc, buf, size);
+    }
+}
+
+#if !defined(_WIN32)
+static void net_pcap_update_fd_handler(NetPcapState *s)
+{
+    qemu_set_fd_handler(s->fd, s->read_poll ? net_pcap_send : NULL, NULL, s);
+}
+
+static void net_pcap_read_poll(NetPcapState *s, bool enable)
+{
+    s->read_poll = enable;
+    net_pcap_update_fd_handler(s);
+}
+#endif
+
+int net_init_pcap(const Netdev *netdev, const char *name, NetClientState *peer,
+                  Error **errp)
+{
+    const NetdevPcapOptions *pcap_opts = &netdev->u.pcap;
+    NetClientState *nc;
+    NetPcapState *s;
+    char err[PCAP_ERRBUF_SIZE];
+    const int promisc = 1;
+    int status;
+
+    pcap_t *p = pcap_open_live(pcap_opts->ifname, 65536, promisc, 1, err);
+    if (p == NULL) {
+        error_setg(errp, "failed to open interface '%s' for capture: %s",
+                   pcap_opts->ifname, err);
+        return -1;
+    }
+
+    status = pcap_set_datalink(p, DLT_EN10MB);
+    if (status != 0) {
+        error_setg(errp, "failed to set data link format to DLT_EN10MB");
+        return -1;
+    }
+
+#ifdef WIN32
+    pcap_setmintocopy(p, 40);
+#endif
+
+    nc = qemu_new_net_client(&net_pcap_info, peer, "pcap", name);
+    s = DO_UPCAST(NetPcapState, nc, nc);
+    s->ifname = strdup(pcap_opts->ifname);
+    s->p = p;
+
+    LOG("Initialized with interface %s", s->ifname);
+
+#ifdef WIN32
+    s->fd = pcap_getevent(p);
+    qemu_add_wait_object(s->fd, net_pcap_send, s);
+#else
+    s->fd = pcap_get_selectable_fd(p);
+    assert(s->fd >= 0);
+    net_pcap_read_poll(s, true);
+#endif
+
+    return 0;
+}

net/pcap.h

@@ -0,0 +1,29 @@
+/*
+ * QEMU libpcap network client
+ *
+ * Copyright (C) 2021 Matt Borgerson
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef NET_PCAP_H
+#define NET_PCAP_H
+
+#include <pcap/pcap.h>
+
+#if defined(_WIN32)
+#include "net/capture_win_ifnames.h"
+#endif
+
+#endif

qapi/net.json

@@ -450,6 +450,19 @@
     '*vhostdev':     'str',
     '*queues':       'int' } }
 
+##
+# @NetdevPcapOptions:
+#
+# Connect a client to a libpcap interface
+#
+# @ifname: Name of host interface
+#
+# Since: 6.0
+##
+{ 'struct': 'NetdevPcapOptions',
+  'data': {
+    'ifname':     'str' } }
+
 ##
 # @NetClientDriver:
 #
@@ -461,7 +474,8 @@
 ##
 { 'enum': 'NetClientDriver',
   'data': [ 'none', 'nic', 'user', 'tap', 'l2tpv3', 'socket', 'vde',
-            'bridge', 'hubport', 'netmap', 'vhost-user', 'vhost-vdpa' ] }
+            'bridge', 'hubport', 'netmap', 'vhost-user', 'vhost-vdpa',
+            'pcap' ] }
 
 ##
 # @Netdev:
@@ -490,7 +504,8 @@
     'hubport':  'NetdevHubPortOptions',
     'netmap':   'NetdevNetmapOptions',
     'vhost-user': 'NetdevVhostUserOptions',
-    'vhost-vdpa': 'NetdevVhostVDPAOptions' } }
+    'vhost-vdpa': 'NetdevVhostVDPAOptions',
+    'pcap':     'NetdevPcapOptions' } }
 
 ##
 # @RxState: