Re: [Qemu-devel] [RFC PATCH V5 2/4] colo-compare: track connection and enqueue packet

[Jason Wang <jasowang@redhat.com>]

On 2016年06月23日 19:34, Zhang Chen wrote:
> In this patch we use kernel jhash table to track
> connection, and then enqueue net packet like this:
>
> + CompareState ++
> |               |
> +---------------+   +---------------+         +---------------+
> |conn list      +--->conn           +--------->conn           |
> +---------------+   +---------------+         +---------------+
> |               |     |           |             |          |
> +---------------+ +---v----+  +---v----+    +---v----+ +---v----+
>                    |primary |  |secondary    |primary | |secondary
>                    |packet  |  |packet  +    |packet  | |packet  +
>                    +--------+  +--------+    +--------+ +--------+
>                        |           |             |          |
>                    +---v----+  +---v----+    +---v----+ +---v----+
>                    |primary |  |secondary    |primary | |secondary
>                    |packet  |  |packet  +    |packet  | |packet  +
>                    +--------+  +--------+    +--------+ +--------+
>                        |           |             |          |
>                    +---v----+  +---v----+    +---v----+ +---v----+
>                    |primary |  |secondary    |primary | |secondary
>                    |packet  |  |packet  +    |packet  | |packet  +
>                    +--------+  +--------+    +--------+ +--------+

A paragraph to describe the above would be more than welcomed.

> Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
> Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> ---
>   include/qemu/jhash.h |  61 ++++++++++++++++
>   net/Makefile.objs    |   1 +
>   net/colo-base.c      | 194 +++++++++++++++++++++++++++++++++++++++++++++++++++
>   net/colo-base.h      |  88 +++++++++++++++++++++++
>   net/colo-compare.c   | 138 +++++++++++++++++++++++++++++++++++-
>   trace-events         |   3 +
>   6 files changed, 483 insertions(+), 2 deletions(-)
>   create mode 100644 include/qemu/jhash.h
>   create mode 100644 net/colo-base.c
>   create mode 100644 net/colo-base.h
>
> diff --git a/include/qemu/jhash.h b/include/qemu/jhash.h
> new file mode 100644
> index 0000000..0fcd875
> --- /dev/null
> +++ b/include/qemu/jhash.h
> @@ -0,0 +1,61 @@
> +/* jhash.h: Jenkins hash support.
> +  *
> +  * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net)
> +  *
> +  * http://burtleburtle.net/bob/hash/
> +  *
> +  * These are the credits from Bob's sources:
> +  *
> +  * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
> +  *
> +  * These are functions for producing 32-bit hashes for hash table lookup.
> +  * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
> +  * are externally useful functions.  Routines to test the hash are
> +included
> +  * if SELF_TEST is defined.  You can use this free for any purpose.
> +It's in
> +  * the public domain.  It has no warranty.
> +  *
> +  * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu)
> +  *
> +  * I've modified Bob's hash to be useful in the Linux kernel, and
> +  * any bugs present are my fault.
> +  * Jozsef
> +  */
> +
> +#ifndef QEMU_JHASH_H__
> +#define QEMU_JHASH_H__
> +
> +#include "qemu/bitops.h"
> +
> +/*
> + * hashtable relation copy from linux kernel jhash
> + */
> +
> +/* __jhash_mix -- mix 3 32-bit values reversibly. */
> +#define __jhash_mix(a, b, c)                \
> +{                                           \
> +    a -= c;  a ^= rol32(c, 4);  c += b;     \
> +    b -= a;  b ^= rol32(a, 6);  a += c;     \
> +    c -= b;  c ^= rol32(b, 8);  b += a;     \
> +    a -= c;  a ^= rol32(c, 16); c += b;     \
> +    b -= a;  b ^= rol32(a, 19); a += c;     \
> +    c -= b;  c ^= rol32(b, 4);  b += a;     \
> +}
> +
> +/* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
> +#define __jhash_final(a, b, c)  \
> +{                               \
> +    c ^= b; c -= rol32(b, 14);  \
> +    a ^= c; a -= rol32(c, 11);  \
> +    b ^= a; b -= rol32(a, 25);  \
> +    c ^= b; c -= rol32(b, 16);  \
> +    a ^= c; a -= rol32(c, 4);   \
> +    b ^= a; b -= rol32(a, 14);  \
> +    c ^= b; c -= rol32(b, 24);  \
> +}
> +
> +/* An arbitrary initial parameter */
> +#define JHASH_INITVAL           0xdeadbeef
> +
> +#endif /* QEMU_JHASH_H__ */

Please split jhash into another patch.

> diff --git a/net/Makefile.objs b/net/Makefile.objs
> index ba92f73..119589f 100644
> --- a/net/Makefile.objs
> +++ b/net/Makefile.objs
> @@ -17,3 +17,4 @@ common-obj-y += filter.o
>   common-obj-y += filter-buffer.o
>   common-obj-y += filter-mirror.o
>   common-obj-y += colo-compare.o
> +common-obj-y += colo-base.o
> diff --git a/net/colo-base.c b/net/colo-base.c
> new file mode 100644
> index 0000000..7e263e8
> --- /dev/null
> +++ b/net/colo-base.c
> @@ -0,0 +1,194 @@
> +/*
> + * COarse-grain LOck-stepping Virtual Machines for Non-stop Service (COLO)
> + * (a.k.a. Fault Tolerance or Continuous Replication)
> + *
> + * Copyright (c) 2016 HUAWEI TECHNOLOGIES CO., LTD.
> + * Copyright (c) 2016 FUJITSU LIMITED
> + * Copyright (c) 2016 Intel Corporation
> + *
> + * Author: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * later.  See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/error-report.h"
> +#include "net/colo-base.h"
> +
> +uint32_t connection_key_hash(const void *opaque)
> +{
> +    const ConnectionKey *key = opaque;
> +    uint32_t a, b, c;
> +
> +    /* Jenkins hash */
> +    a = b = c = JHASH_INITVAL + sizeof(*key);
> +    a += key->src.s_addr;
> +    b += key->dst.s_addr;
> +    c += (key->src_port | key->dst_port << 16);
> +    __jhash_mix(a, b, c);
> +
> +    a += key->ip_proto;
> +    __jhash_final(a, b, c);
> +
> +    return c;
> +}
> +
> +int connection_key_equal(const void *key1, const void *key2)
> +{
> +    return memcmp(key1, key2, sizeof(ConnectionKey)) == 0;
> +}
> +
> +int parse_packet_early(Packet *pkt)
> +{
> +    int network_length;
> +    uint8_t *data = pkt->data;
> +    uint16_t l3_proto;
> +    ssize_t l2hdr_len = eth_get_l2_hdr_length(data);
> +
> +    if (pkt->size < ETH_HLEN) {
> +        error_report("pkt->size < ETH_HLEN");
> +        return 1;
> +    }
> +    pkt->network_layer = data + ETH_HLEN;
> +    l3_proto = eth_get_l3_proto(data, l2hdr_len);
> +    if (l3_proto != ETH_P_IP) {
> +        return 1;
> +    }
> +
> +    network_length = pkt->ip->ip_hl * 4;
> +    if (pkt->size < ETH_HLEN + network_length) {
> +        error_report("pkt->size < network_layer + network_length");
> +        return 1;
> +    }
> +    pkt->transport_layer = pkt->network_layer + network_length;
> +    if (!pkt->transport_layer) {
> +        error_report("pkt->transport_layer is valid");
> +        return 1;
> +    }
> +
> +    return 0;
> +}
> +
> +void fill_connection_key(Packet *pkt, ConnectionKey *key, int mode)
> +{
> +    uint32_t tmp_ports;
> +
> +    key->ip_proto = pkt->ip->ip_p;
> +
> +    switch (key->ip_proto) {
> +    case IPPROTO_TCP:
> +    case IPPROTO_UDP:
> +    case IPPROTO_DCCP:
> +    case IPPROTO_ESP:
> +    case IPPROTO_SCTP:
> +    case IPPROTO_UDPLITE:
> +        tmp_ports = *(uint32_t *)(pkt->transport_layer);
> +        if (mode) {

Looks like mode is unnecessary here, you can actually compare and swap 
duing hashing to avoid mode here.

> +            key->src = pkt->ip->ip_src;
> +            key->dst = pkt->ip->ip_dst;
> +            key->src_port = ntohs(tmp_ports & 0xffff);
> +            key->dst_port = ntohs(tmp_ports >> 16);
> +        } else {
> +            key->dst = pkt->ip->ip_src;
> +            key->src = pkt->ip->ip_dst;
> +            key->dst_port = ntohs(tmp_ports & 0xffff);
> +            key->src_port = ntohs(tmp_ports >> 16);
> +        }
> +        break;
> +    case IPPROTO_AH:
> +        tmp_ports = *(uint32_t *)(pkt->transport_layer + 4);
> +        if (mode) {
> +            key->src = pkt->ip->ip_src;
> +            key->dst = pkt->ip->ip_dst;
> +            key->src_port = ntohs(tmp_ports & 0xffff);
> +            key->dst_port = ntohs(tmp_ports >> 16);
> +        } else {
> +            key->dst = pkt->ip->ip_src;
> +            key->src = pkt->ip->ip_dst;
> +            key->dst_port = ntohs(tmp_ports & 0xffff);
> +            key->src_port = ntohs(tmp_ports >> 16);
> +        }
> +        break;
> +    default:
> +        key->src_port = 0;
> +        key->dst_port = 0;
> +        break;
> +    }
> +}

This seems could be reused, please use a independent patch for 
connection key stuffs.

> +
> +Connection *connection_new(ConnectionKey *key)
> +{
> +    Connection *conn = g_slice_new(Connection);
> +
> +    conn->ip_proto = key->ip_proto;
> +    conn->processing = false;
> +    g_queue_init(&conn->primary_list);
> +    g_queue_init(&conn->secondary_list);
> +
> +    return conn;
> +}
> +
> +void connection_destroy(void *opaque)
> +{
> +    Connection *conn = opaque;
> +
> +    g_queue_foreach(&conn->primary_list, packet_destroy, NULL);
> +    g_queue_free(&conn->primary_list);
> +    g_queue_foreach(&conn->secondary_list, packet_destroy, NULL);
> +    g_queue_free(&conn->secondary_list);
> +    g_slice_free(Connection, conn);
> +}
> +
> +Packet *packet_new(const void *data, int size)
> +{
> +    Packet *pkt = g_slice_new(Packet);
> +
> +    pkt->data = g_memdup(data, size);
> +    pkt->size = size;
> +
> +    return pkt;
> +}
> +
> +void packet_destroy(void *opaque, void *user_data)
> +{
> +    Packet *pkt = opaque;
> +
> +    g_free(pkt->data);
> +    g_slice_free(Packet, pkt);
> +}
> +
> +/*
> + * Clear hashtable, stop this hash growing really huge
> + */
> +void connection_hashtable_reset(GHashTable *connection_track_table)
> +{
> +    g_hash_table_remove_all(connection_track_table);
> +}
> +
> +/* if not found, create a new connection and add to hash table */
> +Connection *connection_get(GHashTable *connection_track_table,
> +                           ConnectionKey *key,
> +                           uint32_t *hashtable_size)
> +{
> +    /* FIXME: protect connection_track_table */

I fail to understand why need protection here.

> +    Connection *conn = g_hash_table_lookup(connection_track_table, key);
> +
> +    if (conn == NULL) {
> +        ConnectionKey *new_key = g_memdup(key, sizeof(*key));
> +
> +        conn = connection_new(key);
> +
> +        (*hashtable_size) += 1;
> +        if (*hashtable_size > HASHTABLE_MAX_SIZE) {
> +            error_report("colo proxy connection hashtable full, clear it");

Is this a hint that we need a synchronization?

> +            connection_hashtable_reset(connection_track_table);
> +            *hashtable_size = 0;
> +            /* TODO:clear conn_list */

If we don't clear conn_list, looks like a bug, so probably need to do 
this in this patch.

> +        }
> +
> +        g_hash_table_insert(connection_track_table, new_key, conn);
> +    }
> +
> +    return conn;
> +}
> diff --git a/net/colo-base.h b/net/colo-base.h
> new file mode 100644
> index 0000000..01c1a5d
> --- /dev/null
> +++ b/net/colo-base.h
> @@ -0,0 +1,88 @@
> +/*
> + * COarse-grain LOck-stepping Virtual Machines for Non-stop Service (COLO)
> + * (a.k.a. Fault Tolerance or Continuous Replication)
> + *
> + * Copyright (c) 2016 HUAWEI TECHNOLOGIES CO., LTD.
> + * Copyright (c) 2016 FUJITSU LIMITED
> + * Copyright (c) 2016 Intel Corporation
> + *
> + * Author: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * later.  See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef QEMU_COLO_BASE_H
> +#define QEMU_COLO_BASE_H
> +
> +#include "slirp/slirp.h"
> +#include "qemu/jhash.h"
> +#include "qemu/rcu.h"

Don't see any rcu usage in this patch.

> +
> +#define HASHTABLE_MAX_SIZE 16384
> +
> +typedef enum colo_conn_state {

This looks like can only take care of TCP, so probably add "tcp" in its 
name.

> +     COLO_CONN_IDLE,
> +
> +    /* States on the primary: For incoming connection */
> +     COLO_CONN_PRI_IN_SYN,   /* Received Syn */
> +     COLO_CONN_PRI_IN_PSYNACK, /* Received syn/ack from primary, but not
> +                                yet from secondary */
> +     COLO_CONN_PRI_IN_SSYNACK, /* Received syn/ack from secondary, but
> +                                  not yet from primary */
> +     COLO_CONN_PRI_IN_SYNACK,  /* Received syn/ack from both */
> +     COLO_CONN_PRI_IN_ESTABLISHED, /* Got the ACK */
> +
> +    /* States on the secondary: For incoming connection */
> +     COLO_CONN_SEC_IN_SYNACK,      /* We sent a syn/ack */
> +     COLO_CONN_SEC_IN_ACK,         /* Saw the ack but didn't yet see our syn/ack */
> +     COLO_CONN_SEC_IN_ESTABLISHED, /* Got the ACK from the outside */

Should we care about any FIN state here?

> +} colo_conn_state;
> +
> +typedef struct Packet {
> +    void *data;
> +    union {
> +        uint8_t *network_layer;
> +        struct ip *ip;
> +    };
> +    uint8_t *transport_layer;
> +    int size;
> +} Packet;

We may start to consider shares codes between e.g hw/net/net_tx_pkt.c.

> +
> +typedef struct ConnectionKey {
> +    /* (src, dst) must be grouped, in the same way than in IP header */
> +    struct in_addr src;
> +    struct in_addr dst;
> +    uint16_t src_port;
> +    uint16_t dst_port;
> +    uint8_t ip_proto;
> +} QEMU_PACKED ConnectionKey;
> +
> +typedef struct Connection {
> +    /* connection primary send queue: element type: Packet */
> +    GQueue primary_list;
> +    /* connection secondary send queue: element type: Packet */
> +    GQueue secondary_list;
> +    /* flag to enqueue unprocessed_connections */
> +    bool processing;
> +    uint8_t ip_proto;
> +    /* be used by filter-rewriter */
> +    colo_conn_state state;
> +    tcp_seq  primary_seq;
> +    tcp_seq  secondary_seq;
> +} Connection;
> +
> +uint32_t connection_key_hash(const void *opaque);
> +int connection_key_equal(const void *opaque1, const void *opaque2);
> +int parse_packet_early(Packet *pkt);
> +void fill_connection_key(Packet *pkt, ConnectionKey *key, int mode);
> +Connection *connection_new(ConnectionKey *key);
> +void connection_destroy(void *opaque);
> +Connection *connection_get(GHashTable *connection_track_table,
> +                           ConnectionKey *key,
> +                           uint32_t *hashtable_size);
> +void connection_hashtable_reset(GHashTable *connection_track_table);
> +Packet *packet_new(const void *data, int size);
> +void packet_destroy(void *opaque, void *user_data);
> +
> +#endif /* QEMU_COLO_BASE_H */
> diff --git a/net/colo-compare.c b/net/colo-compare.c
> index a3e1456..4231fe7 100644
> --- a/net/colo-compare.c
> +++ b/net/colo-compare.c
> @@ -28,6 +28,7 @@
>   #include "qemu/sockets.h"
>   #include "qapi-visit.h"
>   #include "trace.h"
> +#include "net/colo-base.h"
>   
>   #define TYPE_COLO_COMPARE "colo-compare"
>   #define COLO_COMPARE(obj) \
> @@ -38,6 +39,28 @@
>   static QTAILQ_HEAD(, CompareState) net_compares =
>          QTAILQ_HEAD_INITIALIZER(net_compares);
>   
> +/*
> +  + CompareState ++
> +  |               |
> +  +---------------+   +---------------+         +---------------+
> +  |conn list      +--->conn           +--------->conn           |
> +  +---------------+   +---------------+         +---------------+
> +  |               |     |           |             |          |
> +  +---------------+ +---v----+  +---v----+    +---v----+ +---v----+
> +                    |primary |  |secondary    |primary | |secondary
> +                    |packet  |  |packet  +    |packet  | |packet  +
> +                    +--------+  +--------+    +--------+ +--------+
> +                        |           |             |          |
> +                    +---v----+  +---v----+    +---v----+ +---v----+
> +                    |primary |  |secondary    |primary | |secondary
> +                    |packet  |  |packet  +    |packet  | |packet  +
> +                    +--------+  +--------+    +--------+ +--------+
> +                        |           |             |          |
> +                    +---v----+  +---v----+    +---v----+ +---v----+
> +                    |primary |  |secondary    |primary | |secondary
> +                    |packet  |  |packet  +    |packet  | |packet  +
> +                    +--------+  +--------+    +--------+ +--------+
> +*/
>   typedef struct CompareState {
>       Object parent;
>   
> @@ -50,12 +73,103 @@ typedef struct CompareState {
>       QTAILQ_ENTRY(CompareState) next;
>       SocketReadState pri_rs;
>       SocketReadState sec_rs;
> +
> +    /* connection list: the connections belonged to this NIC could be found
> +     * in this list.
> +     * element type: Connection
> +     */
> +    GQueue conn_list;
> +    QemuMutex conn_list_lock; /* to protect conn_list */

Why need this mutex?

> +    /* hashtable to save connection */
> +    GHashTable *connection_track_table;
> +    /* to save unprocessed_connections */
> +    GQueue unprocessed_connections;
> +    /* proxy current hash size */
> +    uint32_t hashtable_size;
>   } CompareState;
>   
>   typedef struct CompareClass {
>       ObjectClass parent_class;
>   } CompareClass;
>   
> +enum {
> +    PRIMARY_IN = 0,
> +    SECONDARY_IN,
> +};
> +
> +static int compare_chr_send(CharDriverState *out,
> +                            const uint8_t *buf,
> +                            uint32_t size);
> +
> +/*
> + * Return 0 on success, if return -1 means the pkt
> + * is unsupported(arp and ipv6) and will be sent later
> + */
> +static int packet_enqueue(CompareState *s, int mode)
> +{
> +    ConnectionKey key = {{ 0 } };
> +    Packet *pkt = NULL;
> +    Connection *conn;
> +
> +    if (mode == PRIMARY_IN) {
> +        pkt = packet_new(s->pri_rs.buf, s->pri_rs.packet_len);
> +    } else {
> +        pkt = packet_new(s->sec_rs.buf, s->sec_rs.packet_len);
> +    }
> +
> +    if (parse_packet_early(pkt)) {
> +        packet_destroy(pkt, NULL);
> +        pkt = NULL;
> +        return -1;
> +    }
> +    fill_connection_key(pkt, &key, PRIMARY_IN);
> +
> +    conn = connection_get(s->connection_track_table,
> +                          &key,
> +                          &s->hashtable_size);
> +    if (!conn->processing) {
> +        qemu_mutex_lock(&s->conn_list_lock);
> +        g_queue_push_tail(&s->conn_list, conn);
> +        qemu_mutex_unlock(&s->conn_list_lock);
> +        conn->processing = true;
> +    }
> +
> +    if (mode == PRIMARY_IN) {
> +        g_queue_push_tail(&conn->primary_list, pkt);
> +    } else {
> +        g_queue_push_tail(&conn->secondary_list, pkt);
> +    }
> +
> +    return 0;
> +}
> +
> +static int compare_chr_send(CharDriverState *out,
> +                            const uint8_t *buf,
> +                            uint32_t size)
> +{
> +    int ret = 0;
> +    uint32_t len = htonl(size);
> +
> +    if (!size) {
> +        return 0;
> +    }
> +
> +    ret = qemu_chr_fe_write_all(out, (uint8_t *)&len, sizeof(len));
> +    if (ret != sizeof(len)) {
> +        goto err;
> +    }
> +
> +    ret = qemu_chr_fe_write_all(out, (uint8_t *)buf, size);
> +    if (ret != size) {
> +        goto err;
> +    }
> +
> +    return 0;
> +
> +err:
> +    return ret < 0 ? ret : -EIO;
> +}
> +
>   static char *compare_get_pri_indev(Object *obj, Error **errp)
>   {
>       CompareState *s = COLO_COMPARE(obj);
> @@ -103,12 +217,21 @@ static void compare_set_outdev(Object *obj, const char *value, Error **errp)
>   
>   static void compare_pri_rs_finalize(SocketReadState *pri_rs)
>   {
> -    /* if packet_enqueue pri pkt failed we will send unsupported packet */
> +    CompareState *s = container_of(pri_rs, CompareState, pri_rs);
> +
> +    if (packet_enqueue(s, PRIMARY_IN)) {
> +        trace_colo_compare_main("primary: unsupported packet in");
> +        compare_chr_send(s->chr_out, pri_rs->buf, pri_rs->packet_len);
> +    }

Do we have a upper limit on the maximum numbers of packets could be 
queued? If not, guest may easily trigger OOM.

>   }
>   
>   static void compare_sec_rs_finalize(SocketReadState *sec_rs)
>   {
> -    /* if packet_enqueue sec pkt failed we will notify trace */
> +    CompareState *s = container_of(sec_rs, CompareState, sec_rs);
> +
> +    if (packet_enqueue(s, SECONDARY_IN)) {
> +        trace_colo_compare_main("secondary: unsupported packet in");
> +    }
>   }
>   
>   /*
> @@ -161,6 +284,15 @@ static void colo_compare_complete(UserCreatable *uc, Error **errp)
>       net_socket_rs_init(&s->pri_rs, compare_pri_rs_finalize);
>       net_socket_rs_init(&s->sec_rs, compare_sec_rs_finalize);
>   
> +    g_queue_init(&s->conn_list);
> +    qemu_mutex_init(&s->conn_list_lock);
> +    s->hashtable_size = 0;
> +
> +    s->connection_track_table = g_hash_table_new_full(connection_key_hash,
> +                                                      connection_key_equal,
> +                                                      g_free,
> +                                                      connection_destroy);
> +
>       return;
>   }
>   
> @@ -203,6 +335,8 @@ static void colo_compare_finalize(Object *obj)
>       if (!QTAILQ_EMPTY(&net_compares)) {
>           QTAILQ_REMOVE(&net_compares, s, next);
>       }
> +    qemu_mutex_destroy(&s->conn_list_lock);
> +    g_queue_free(&s->conn_list);
>   
>       g_free(s->pri_indev);
>       g_free(s->sec_indev);
> diff --git a/trace-events b/trace-events
> index ca7211b..703de1a 100644
> --- a/trace-events
> +++ b/trace-events
> @@ -1916,3 +1916,6 @@ aspeed_vic_update_fiq(int flags) "Raising FIQ: %d"
>   aspeed_vic_update_irq(int flags) "Raising IRQ: %d"
>   aspeed_vic_read(uint64_t offset, unsigned size, uint32_t value) "From 0x%" PRIx64 " of size %u: 0x%" PRIx32
>   aspeed_vic_write(uint64_t offset, unsigned size, uint32_t data) "To 0x%" PRIx64 " of size %u: 0x%" PRIx32
> +
> +# net/colo-compare.c
> +colo_compare_main(const char *chr) ": %s"