Re: [Qemu-devel] [PATCH v4] qemu-ga: Add guest-network-info command

[Luiz Capitulino]

On Sun, 19 Feb 2012 12:15:43 +0100
Michal Privoznik <address@hidden> wrote:

> This command returns an array of:
> 
>  [ifname, ipaddr, ipaddr_family, prefix, hwaddr]
> 
> for each interface in the system that has an IP address.
> Currently, only IPv4 and IPv6 are supported.
> 
> Signed-off-by: Michal Privoznik <address@hidden>
> ---
> diff to v3:
> -use ctpop32() instead of separate count_one_bits()
> 
> diff to v2:
> -Properly set IP addr family for IPv6
> 
> diff to v1:
> -move from guest-getip to guest-network-info
> -replace black boxed algorithm for population count
> -several coding styles improvements
>  qapi-schema-guest.json     |   29 ++++++++
>  qga/guest-agent-commands.c |  157 
> ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 186 insertions(+), 0 deletions(-)
> 
> diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json
> index 5f8a18d..ca4fdc5 100644
> --- a/qapi-schema-guest.json
> +++ b/qapi-schema-guest.json
> @@ -219,3 +219,32 @@
>  ##
>  { 'command': 'guest-fsfreeze-thaw',
>    'returns': 'int' }
> +
> +##
> +# @guest-network-info:
> +#
> +# Get list of guest IP addresses, MAC addresses
> +# and netmasks.
> +#
> +# @name: The name of interface for which info are being delivered
> +#
> +# @ipaddr: IP address assigned to @name
> +#
> +# @ipaddrtype: Type of @ipaddr (e.g. ipv4, ipv6)
> +#
> +# @prefix: Network prefix length
> +#
> +# @hwaddr: Hardware address of @name
> +#
> +# Returns: List of GuestNetworkInfo on success.
> +#
> +# Since: 1.1
> +##
> +{ 'enum': 'GuestIpAddrType',
> +  'data': [ 'ipv4', 'ipv6' ] }
> +{ 'type': 'GuestNetworkInfo',
> +  'data': {'iface': {'name': 'str', 'ipaddr': 'str',
> +                     'ipaddrtype': 'GuestIpAddrType',
> +                     'prefix': 'int', 'hwaddr': 'str'} } }
> +{ 'command': 'guest-network-info',
> +  'returns': ['GuestNetworkInfo'] }

No need for short names like 'ipaddr', longer names like 'ip-address' are 
better.

Also, please, document the enum, the type and the command separately. You can 
look
for examples in the qapi-schema.json file (yes, we're not doing it in this 
file, but
we should).

Do we really need the 'iface' dict, btw?

> diff --git a/qga/guest-agent-commands.c b/qga/guest-agent-commands.c
> index a09c8ca..1371f8b 100644
> --- a/qga/guest-agent-commands.c
> +++ b/qga/guest-agent-commands.c
> @@ -5,6 +5,7 @@
>   *
>   * Authors:
>   *  Michael Roth      <address@hidden>
> + *  Michal Privoznik  <address@hidden>
>   *
>   * This work is licensed under the terms of the GNU GPL, version 2 or later.
>   * See the COPYING file in the top-level directory.
> @@ -23,10 +24,15 @@
>  
>  #include <sys/types.h>
>  #include <sys/ioctl.h>
> +#include <ifaddrs.h>
> +#include <arpa/inet.h>
> +#include <sys/socket.h>
> +#include <net/if.h>
>  #include "qga/guest-agent-core.h"
>  #include "qga-qmp-commands.h"
>  #include "qerror.h"
>  #include "qemu-queue.h"
> +#include "host-utils.h"
>  
>  static GAState *ga_state;
>  
> @@ -583,3 +589,154 @@ void ga_command_state_init(GAState *s, GACommandState 
> *cs)
>  #endif
>      ga_command_state_add(cs, guest_file_init, NULL);
>  }
> +
> +/*
> + * Get the list of interfaces among with their
> + * IP/MAC addresses, prefixes and IP versions
> + */
> +GuestNetworkInfoList *qmp_guest_network_info(Error **err)
> +{
> +    GuestNetworkInfoList *head = NULL, *cur_item = NULL;
> +    struct ifaddrs *ifap = NULL, *ifa = NULL;
> +    char err_msg[512];
> +
> +    g_debug("guest-network-info called");
> +
> +    if (getifaddrs(&ifap) < 0) {
> +        snprintf(err_msg, sizeof(err_msg),
> +                 "getifaddrs failed : %s", strerror(errno));
> +        error_set(err, QERR_QGA_COMMAND_FAILED, err_msg);
> +        goto error;
> +    }

Generic errors are bad for the user. The best thing to do would be to have a 
QERR_
for the possible errors getifaddrs() can return. However, getifaddrs() can 
return
errors from several functions, so I don't know what's the best thing to do here.

Ideas, Michael?

> +
> +    ifa = ifap;
> +    while (ifa) {
> +        GuestNetworkInfoList *info = NULL;
> +        char addr4[INET_ADDRSTRLEN];
> +        char addr6[INET6_ADDRSTRLEN];
> +        unsigned char *mac_addr;
> +        void *tmp_addr_ptr = NULL;

I'd call this just *p.

> +        int sock, family;
> +        int mac_supported;
> +        struct ifreq ifr;
> +
> +        /* Step over interfaces without an address */
> +        if (!ifa->ifa_addr) {
> +            ifa = ifa->ifa_next;
> +            continue;
> +        }

This matches the documentation, but wouldn't it be better to return information
about _interfaces_ (vs. _ip addresses_)? We could make the ip-address field
optional then.

> +
> +        g_debug("Processing %s interface", ifa->ifa_name);
> +
> +        family = ifa->ifa_addr->sa_family;
> +
> +        if (family == AF_INET) {
> +            /* interface with IPv4 address */
> +            tmp_addr_ptr = &((struct sockaddr_in *)ifa->ifa_addr)->sin_addr;
> +            inet_ntop(AF_INET, tmp_addr_ptr, addr4, sizeof(addr4));

inet_ntop() can fail.

> +
> +            info = g_malloc0(sizeof(*info));
> +            info->value = g_malloc0(sizeof(*info->value));
> +            info->value->iface.name = g_strdup(ifa->ifa_name);

The three lines above can be moved outside the if else block.

> +            info->value->iface.ipaddr = g_strdup(addr4);
> +            info->value->iface.ipaddrtype = GUEST_IP_ADDR_TYPE_IPV4;
> +
> +            /* Count the number of set bits in netmask.
> +             * This is safe as '1' and '0' cannot be shuffled in netmask. */
> +            tmp_addr_ptr = &((struct sockaddr_in 
> *)ifa->ifa_netmask)->sin_addr;
> +            info->value->iface.prefix =
> +                ctpop32(((uint32_t *) tmp_addr_ptr)[0]);
> +        } else if (family == AF_INET6) {
> +            /* interface with IPv6 address */
> +            tmp_addr_ptr = &((struct sockaddr_in6 
> *)ifa->ifa_addr)->sin6_addr;
> +            inet_ntop(AF_INET6, tmp_addr_ptr, addr6, sizeof(addr6));
> +
> +            info = g_malloc0(sizeof(*info));
> +            info->value = g_malloc0(sizeof(*info->value));
> +            info->value->iface.name = g_strdup(ifa->ifa_name);
> +            info->value->iface.ipaddr = g_strdup(addr6);
> +            info->value->iface.ipaddrtype = GUEST_IP_ADDR_TYPE_IPV6;
> +
> +            /* Count the number of set bits in netmask.
> +             * This is safe as '1' and '0' cannot be shuffled in netmask. */
> +            tmp_addr_ptr = &((struct sockaddr_in6 
> *)ifa->ifa_netmask)->sin6_addr;
> +            info->value->iface.prefix =
> +                ctpop32(((uint32_t *) tmp_addr_ptr)[0]) +
> +                ctpop32(((uint32_t *) tmp_addr_ptr)[1]) +
> +                ctpop32(((uint32_t *) tmp_addr_ptr)[2]) +
> +                ctpop32(((uint32_t *) tmp_addr_ptr)[3]);
> +        }
> +
> +        /* Add new family here */

The comment is not needed.

> +
> +        mac_supported = ifa->ifa_flags & SIOCGIFHWADDR;
> +
> +        ifa = ifa->ifa_next;
> +
> +        if (!info) {
> +            continue;
> +        }

How can info be NULL here?

> +
> +        if (!cur_item) {
> +            head = cur_item = info;
> +        } else {
> +            cur_item->next = info;
> +            cur_item = info;
> +        }
> +
> +        g_debug("Appending to return: iface=%s, ip=%s, type=%llu,  
> prefix=%llu",
> +                info->value->iface.name,
> +                info->value->iface.ipaddr,
> +                (unsigned long long) info->value->iface.ipaddrtype,
> +                (unsigned long long) info->value->iface.prefix);
> +
> +        /* If we can't get get MAC address on this interface,
> +         * don't even try but continue to another interface */
> +        if (!mac_supported) {
> +            continue;
> +        }

Is 'mac_supported' really needed? I'd just do 'ifa->ifa_flags & SIOCGIFHWADDR'.

> +
> +        sock = socket(PF_INET, SOCK_STREAM, 0);
> +
> +        if (sock == -1) {
> +            snprintf(err_msg, sizeof(err_msg),
> +                     "failed to create socket: %s", strerror(errno));
> +            error_set(err, QERR_QGA_COMMAND_FAILED, err_msg);
> +            goto error;
> +        }

Generic error.

> +
> +        memset(&ifr, 0, sizeof(ifr));
> +        strncpy(ifr.ifr_name,  info->value->iface.name, IF_NAMESIZE);
> +        if (ioctl(sock, SIOCGIFHWADDR, &ifr) == -1) {
> +            snprintf(err_msg, sizeof(err_msg),
> +                     "failed to get MAC addres of %s: %s",
> +                     info->value->iface.name,
> +                     strerror(errno));
> +            error_set(err, QERR_QGA_COMMAND_FAILED, err_msg);
> +            goto error;
> +        }

Generic error.

> +
> +        mac_addr = (unsigned char *) &ifr.ifr_hwaddr.sa_data;
> +
> +        if (asprintf(&info->value->iface.hwaddr,
> +                     "%02x:%02x:%02x:%02x:%02x:%02x",
> +                     (int) mac_addr[0], (int) mac_addr[1],
> +                     (int) mac_addr[2], (int) mac_addr[3],
> +                     (int) mac_addr[4], (int) mac_addr[5]) == -1) {
> +            snprintf(err_msg, sizeof(err_msg),
> +                     "failed to format MAC: %s", strerror(errno));
> +            error_set(err, QERR_QGA_COMMAND_FAILED, err_msg);
> +            goto error;
> +        }
> +
> +        close(sock);
> +    }
> +
> +    freeifaddrs(ifap);
> +    return head;
> +
> +error:
> +    freeifaddrs(ifap);
> +    qapi_free_GuestNetworkInfoList(head);
> +    return NULL;
> +}