Introduced "snaplen=<length>" option. It is convenient to truncate
large packets to only capture necessary headers.

Signed-off-by: Zhike Wang <wangzh...@jd.com>
---
 app/pdump/main.c                       | 32 ++++++++++++++++++++++++++-
 doc/guides/rel_notes/release_20_08.rst |  4 ++++
 doc/guides/tools/pdump.rst             |  5 ++++-
 drivers/net/pcap/rte_eth_pcap.c        | 40 ++++++++++++++++++++++++++++++++--
 4 files changed, 77 insertions(+), 4 deletions(-)

diff --git a/app/pdump/main.c b/app/pdump/main.c
index c38c537..1f87310 100644
--- a/app/pdump/main.c
+++ b/app/pdump/main.c
@@ -41,10 +41,12 @@
 #define PDUMP_RING_SIZE_ARG "ring-size"
 #define PDUMP_MSIZE_ARG "mbuf-size"
 #define PDUMP_NUM_MBUFS_ARG "total-num-mbufs"
+#define PDUMP_SNAPLEN_ARG "snaplen"
 
 #define VDEV_NAME_FMT "net_pcap_%s_%d"
 #define VDEV_PCAP_ARGS_FMT "tx_pcap=%s"
 #define VDEV_IFACE_ARGS_FMT "tx_iface=%s"
+#define VDEV_SNAPLEN_ARGS_FMT "snaplen=%d"
 #define TX_STREAM_SIZE 64
 
 #define MP_NAME "pdump_pool_%d"
@@ -97,6 +99,7 @@ enum pdump_by {
        PDUMP_RING_SIZE_ARG,
        PDUMP_MSIZE_ARG,
        PDUMP_NUM_MBUFS_ARG,
+       PDUMP_SNAPLEN_ARG,
        NULL
 };
 
@@ -116,6 +119,7 @@ struct pdump_tuples {
        uint32_t ring_size;
        uint16_t mbuf_data_size;
        uint32_t total_num_mbufs;
+       uint16_t snaplen;
 
        /* params for library API call */
        uint32_t dir;
@@ -160,7 +164,8 @@ struct parse_val {
                        " tx-dev=<iface or pcap file>,"
                        "[ring-size=<ring size>default:16384],"
                        "[mbuf-size=<mbuf data size>default:2176],"
-                       "[total-num-mbufs=<number of mbufs>default:65535]'\n",
+                       "[total-num-mbufs=<number of mbufs>default:65535],"
+                       "[snaplen=<snap length>default:0, meaning no 
truncation]'\n",
                        prgname);
 }
 
@@ -370,6 +375,19 @@ struct parse_val {
        } else
                pt->total_num_mbufs = MBUFS_PER_POOL;
 
+       /* snaplen parsing and validation */
+       cnt1 = rte_kvargs_count(kvlist, PDUMP_SNAPLEN_ARG);
+       if (cnt1 == 1) {
+               v.min = 1;
+               v.max = UINT16_MAX;
+               ret = rte_kvargs_process(kvlist, PDUMP_SNAPLEN_ARG,
+                                               &parse_uint_value, &v);
+               if (ret < 0)
+                       goto free_kvlist;
+               pt->snaplen = (uint16_t) v.val;
+       } else
+               pt->snaplen = 0;
+
        num_tuples++;
 
 free_kvlist:
@@ -692,6 +710,9 @@ struct parse_val {
                                 VDEV_IFACE_ARGS_FMT, pt->rx_dev) :
                        snprintf(vdev_args, sizeof(vdev_args),
                                 VDEV_PCAP_ARGS_FMT, pt->rx_dev);
+                       snprintf(vdev_args + strlen(vdev_args),
+                                sizeof(vdev_args) - strlen(vdev_args),
+                                ","VDEV_SNAPLEN_ARGS_FMT, pt->snaplen);
                        if (rte_eal_hotplug_add("vdev", vdev_name,
                                                vdev_args) < 0) {
                                cleanup_rings();
@@ -722,6 +743,9 @@ struct parse_val {
                                         VDEV_IFACE_ARGS_FMT, pt->tx_dev) :
                                snprintf(vdev_args, sizeof(vdev_args),
                                         VDEV_PCAP_ARGS_FMT, pt->tx_dev);
+                               snprintf(vdev_args + strlen(vdev_args),
+                                        sizeof(vdev_args) - strlen(vdev_args),
+                                        ","VDEV_SNAPLEN_ARGS_FMT, pt->snaplen);
                                if (rte_eal_hotplug_add("vdev", vdev_name,
                                                        vdev_args) < 0) {
                                        cleanup_rings();
@@ -762,6 +786,9 @@ struct parse_val {
                                 VDEV_IFACE_ARGS_FMT, pt->rx_dev) :
                        snprintf(vdev_args, sizeof(vdev_args),
                                 VDEV_PCAP_ARGS_FMT, pt->rx_dev);
+                       snprintf(vdev_args + strlen(vdev_args),
+                                sizeof(vdev_args) - strlen(vdev_args),
+                                ","VDEV_SNAPLEN_ARGS_FMT, pt->snaplen);
                        if (rte_eal_hotplug_add("vdev", vdev_name,
                                                vdev_args) < 0) {
                                cleanup_rings();
@@ -799,6 +826,9 @@ struct parse_val {
                                 VDEV_IFACE_ARGS_FMT, pt->tx_dev) :
                        snprintf(vdev_args, sizeof(vdev_args),
                                 VDEV_PCAP_ARGS_FMT, pt->tx_dev);
+                       snprintf(vdev_args + strlen(vdev_args),
+                                sizeof(vdev_args) - strlen(vdev_args),
+                                ","VDEV_SNAPLEN_ARGS_FMT, pt->snaplen);
                        if (rte_eal_hotplug_add("vdev", vdev_name,
                                                vdev_args) < 0) {
                                cleanup_rings();
diff --git a/doc/guides/rel_notes/release_20_08.rst 
b/doc/guides/rel_notes/release_20_08.rst
index 17d70e7..462c4f3 100644
--- a/doc/guides/rel_notes/release_20_08.rst
+++ b/doc/guides/rel_notes/release_20_08.rst
@@ -171,6 +171,10 @@ New Features
   See the :doc:`../sample_app_ug/l2_forward_real_virtual` for more
   details of this parameter usage.
 
+* **Added a devarg to truncate the dumped packets for PCAP vdev.**
+
+  A new devarg ``snaplen`` was introduced to allow users to truncate the
+  dumped packets, and is convenient for capturing with large packet size.
 
 Removed Items
 -------------
diff --git a/doc/guides/tools/pdump.rst b/doc/guides/tools/pdump.rst
index 8a499c6..27b9102 100644
--- a/doc/guides/tools/pdump.rst
+++ b/doc/guides/tools/pdump.rst
@@ -45,7 +45,8 @@ The tool has a number of command line options:
                                     tx-dev=<iface or pcap file>),
                                    [ring-size=<ring size>],
                                    [mbuf-size=<mbuf data size>],
-                                   [total-num-mbufs=<number of mbufs>]'
+                                   [total-num-mbufs=<number of mbufs>],
+                                   [snaplen=<snap length>]'
 
 The ``--multi`` command line option is optional argument. If passed, capture
 will be running on unique cores for all ``--pdump`` options. If ignored,
@@ -114,6 +115,8 @@ default size 2176.
 Total number mbufs in mempool. This is used internally for mempool creation. 
This is an optional parameter with default
 value 65535.
 
+``snaplen``:
+Truncate snaplen bytes of data from each packet. This is an optional parameter 
with default value 0, meaning no truncation.
 
 Example
 -------
diff --git a/drivers/net/pcap/rte_eth_pcap.c b/drivers/net/pcap/rte_eth_pcap.c
index 668cbd1..0d2a4b3 100644
--- a/drivers/net/pcap/rte_eth_pcap.c
+++ b/drivers/net/pcap/rte_eth_pcap.c
@@ -40,6 +40,7 @@
 #define ETH_PCAP_IFACE_ARG    "iface"
 #define ETH_PCAP_PHY_MAC_ARG  "phy_mac"
 #define ETH_PCAP_INFINITE_RX_ARG  "infinite_rx"
+#define ETH_PCAP_SNAPLEN_ARG  "snaplen"
 
 #define ETH_PCAP_ARG_MAXLEN    64
 
@@ -86,6 +87,7 @@ struct pmd_internals {
        int single_iface;
        int phy_mac;
        unsigned int infinite_rx;
+       unsigned int snaplen;
 };
 
 struct pmd_process_private {
@@ -114,6 +116,7 @@ struct pmd_devargs_all {
        unsigned int is_rx_pcap;
        unsigned int is_rx_iface;
        unsigned int infinite_rx;
+       unsigned int snaplen;
 };
 
 static const char *valid_arguments[] = {
@@ -125,6 +128,7 @@ struct pmd_devargs_all {
        ETH_PCAP_IFACE_ARG,
        ETH_PCAP_PHY_MAC_ARG,
        ETH_PCAP_INFINITE_RX_ARG,
+       ETH_PCAP_SNAPLEN_ARG,
        NULL
 };
 
@@ -322,11 +326,13 @@ struct pmd_devargs_all {
        pcap_dumper_t *dumper;
        unsigned char temp_data[RTE_ETH_PCAP_SNAPLEN];
        size_t len, caplen;
+       struct pmd_internals *internal;
 
        pp = rte_eth_devices[dumper_q->port_id].process_private;
        dumper = pp->tx_dumper[dumper_q->queue_id];
+       internal = rte_eth_devices[dumper_q->port_id].data->dev_private;
 
-       if (dumper == NULL || nb_pkts == 0)
+       if (dumper == NULL || nb_pkts == 0 || internal == NULL)
                return 0;
 
        /* writes the nb_pkts packets to the previously opened pcap file
@@ -339,6 +345,9 @@ struct pmd_devargs_all {
                        caplen = sizeof(temp_data);
                }
 
+               if (caplen > internal->snaplen)
+                       caplen = internal->snaplen;
+
                calculate_timestamp(&header.ts);
                header.len = len;
                header.caplen = caplen;
@@ -1083,6 +1092,21 @@ struct pmd_devargs_all {
 }
 
 static int
+get_snaplen_arg(const char *key __rte_unused,
+               const char *value, void *extra_args)
+{
+       if (extra_args) {
+               unsigned int snaplen = (unsigned int)atoi(value);
+               unsigned int *snaplen_p = extra_args;
+
+               if (snaplen == 0)
+                       snaplen = RTE_ETH_PCAP_SNAPLEN;
+               *snaplen_p = snaplen;
+       }
+       return 0;
+}
+
+static int
 pmd_init_internals(struct rte_vdev_device *vdev,
                const unsigned int nb_rx_queues,
                const unsigned int nb_tx_queues,
@@ -1291,6 +1315,9 @@ struct pmd_devargs_all {
        /* store weather we are using a single interface for rx/tx or not */
        internals->single_iface = single_iface;
 
+       if (devargs_all->is_tx_pcap)
+               internals->snaplen = devargs_all->snaplen;
+
        if (single_iface) {
                internals->if_index = if_nametoindex(rx_queues->queue[0].name);
 
@@ -1341,6 +1368,7 @@ struct pmd_devargs_all {
                .is_tx_pcap = 0,
                .is_tx_iface = 0,
                .infinite_rx = 0,
+               .snaplen = RTE_ETH_PCAP_SNAPLEN,
        };
 
        name = rte_vdev_device_name(dev);
@@ -1464,6 +1492,13 @@ struct pmd_devargs_all {
        if (ret < 0)
                goto free_kvlist;
 
+       if (devargs_all.is_tx_pcap) {
+               ret = rte_kvargs_process(kvlist, ETH_PCAP_SNAPLEN_ARG,
+                               &get_snaplen_arg, &devargs_all.snaplen);
+               if (ret < 0)
+                       goto free_kvlist;
+       }
+
        /*
         * We check whether we want to open a TX stream to a real NIC,
         * a pcap file, or drop packets on tx
@@ -1587,4 +1622,5 @@ struct pmd_devargs_all {
        ETH_PCAP_TX_IFACE_ARG "=<ifc> "
        ETH_PCAP_IFACE_ARG "=<ifc> "
        ETH_PCAP_PHY_MAC_ARG "=<int>"
-       ETH_PCAP_INFINITE_RX_ARG "=<0|1>");
+       ETH_PCAP_INFINITE_RX_ARG "=<0|1>"
+       ETH_PCAP_SNAPLEN_ARG "=<int>");
-- 
1.8.3.1


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