Re: [Qemu-devel] [PATCH 1/1] Support abstract socket namespace in AF_UNIX socket family.

[Alexander Barabash <alexander_barabash@mentor.com>]

Hi,

On 01/07/2013 04:07 PM, Anthony Liguori wrote:
> Alexander Barabash <alexander_barabash@mentor.com> writes:
>
>> The abstract socket namespace is a nonportable Linux extension.
>> The sockets' names in this namespace have no connection
>> with file system pathnames. To specify a named AF_UNIX socket
>> in the abstract socket namespace, start the socket's path option
>> with a backslash followed by zero: \0.
>>
>> Signed-off-by: Alexander Barabash <alexander_barabash@mentor.com>
> Magic interpretation of path names is a bad thing in general.
>
> I think it would be better to add a flag 'abstract=on' which
> indicates to use the abstract namespace.  As an example:
>
> qemu -chardev foo,path=bar,abstract=on
>
> vs:
>
> qemu -chardev foo,path="\\\\0bar"
>
> I think the former is quite a bit more user friendly.
OK

>
> Regards,
>
> Anthony Liguori
Regards,
Alex
>
>> ---
>>   qemu-sockets.c |   58 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
>>   1 file changed, 55 insertions(+), 3 deletions(-)
>>
>> diff --git a/qemu-sockets.c b/qemu-sockets.c
>> index 3537bf3..70c8ad5 100644
>> --- a/qemu-sockets.c
>> +++ b/qemu-sockets.c
>> @@ -663,11 +663,50 @@ int inet_nonblocking_connect(const char *str,
>>   
>>   #ifndef _WIN32
>>   
>> +/*
>> + * The abstract socket namespace is a nonportable Linux extension.
>> + * The sockets' names in this namespace have no connection
>> + * with file system pathnames. To specify a named AF_UNIX socket
>> + * in the abstract socket namespace, start the socket's path option
>> + * with a backslash followed by zero: \0.
>> + */
>> +static
>> +char *get_abstract_namespace_path(const char *path, int *abstract_path_length)
>> +{
>> +    char *abstract_path;
>> +    char *inp;
>> +    char *outp;
>> +    char c;
>> +
>> +    *abstract_path_length = 0;
>> +    if ((path == NULL) || (path[0] != '\\') || (path[1] != '0')) {
>> +        return NULL;
>> +    }
>> +    abstract_path = g_strdup(path + 2);
>> +    for (inp = abstract_path, outp = abstract_path; (c = *inp); ++inp, ++outp) {
>> +        if (c == '\\') {
>> +            c = *++inp;
>> +            if (c == '\\') {
>> +                *outp = c;
>> +            } else if (c == '0') {
>> +                *outp = '\0';
>> +            }
>> +        } else {
>> +            *outp = c;
>> +        }
>> +    }
>> +    *abstract_path_length = outp - abstract_path;
>> +    return abstract_path;
>> +}
>> +
>>   int unix_listen_opts(QemuOpts *opts, Error **errp)
>>   {
>>       struct sockaddr_un un;
>>       const char *path = qemu_opt_get(opts, "path");
>> +    int abstract_path_length;
>> +    char *abstract_path;
>>       int sock, fd;
>> +    socklen_t addrlen = sizeof(un);
>>   
>>       sock = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
>>       if (sock < 0) {
>> @@ -675,9 +714,18 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
>>           return -1;
>>       }
>>   
>> +    abstract_path = get_abstract_namespace_path(path, &abstract_path_length);
>> +
>>       memset(&un, 0, sizeof(un));
>>       un.sun_family = AF_UNIX;
>> -    if (path && strlen(path)) {
>> +    if (abstract_path != NULL) {
>> +        if (abstract_path_length > sizeof(un.sun_path) - 1) {
>> +            abstract_path_length = sizeof(un.sun_path) - 1;
>> +        }
>> +        memcpy(un.sun_path + 1, abstract_path, abstract_path_length);
>> +        addrlen =
>> +            offsetof(struct sockaddr_un, sun_path) + 1 + abstract_path_length;
>> +    } else if (path && strlen(path)) {
>>           snprintf(un.sun_path, sizeof(un.sun_path), "%s", path);
>>       } else {
>>           char *tmpdir = getenv("TMPDIR");
>> @@ -694,8 +742,10 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
>>           qemu_opt_set(opts, "path", un.sun_path);
>>       }
>>   
>> -    unlink(un.sun_path);
>> -    if (bind(sock, (struct sockaddr*) &un, sizeof(un)) < 0) {
>> +    if (abstract_path == NULL) {
>> +        unlink(un.sun_path);
>> +    }
>> +    if (bind(sock, (struct sockaddr *) &un, addrlen) < 0) {
>>           error_set_errno(errp, errno, QERR_SOCKET_BIND_FAILED);
>>           goto err;
>>       }
>> @@ -704,10 +754,12 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
>>           goto err;
>>       }
>>   
>> +    g_free(abstract_path);
>>       return sock;
>>   
>>   err:
>>       closesocket(sock);
>> +    g_free(abstract_path);
>>       return -1;
>>   }
>>   
>> -- 
>> 1.7.9.5