Re: [Qemu-devel] [PATCH] slirp: add 'cmd:' target for guestfwd

[Jan Kiszka]

On 2012-05-31 01:08, Alexander Graf wrote:
> 
> On 04.06.2011, at 08:12, Alexander Graf wrote:
> 
>> When using guestfwd=, Qemu only connects the virtual server's TCP port
>> to a single chardev. This is useless in most cases, as we usually want
>> to have more than a single connection from the guest to the outside world.
>>
>> This patch adds a new cmd: target to guestfwd= that allows for execution
>> of a command on every TCP connection. This leverages the same code as
>> the -smb parameter, just that here the command is user defined.
>>
>> Reported-by: Sascha Wilde <address@hidden>
>> Signed-off-by: Alexander Graf <address@hidden>
> 
> 
> Ping?

No general concerns, but it no longer applies. Some first comments below.

> 
> 
> Alex
> 
>> ---
>> net/slirp.c     |   44 ++++++++++++++++++++++++++++----------------
>> qemu-options.hx |   20 +++++++++++++++++++-
>> 2 files changed, 47 insertions(+), 17 deletions(-)
>>
>> diff --git a/net/slirp.c b/net/slirp.c
>> index e057a14..4e4e3c3 100644
>> --- a/net/slirp.c
>> +++ b/net/slirp.c
>> @@ -615,25 +615,37 @@ static int slirp_guestfwd(SlirpState *s, const char 
>> *config_str,
>>
>>     fwd = qemu_malloc(sizeof(struct GuestFwd));
>>     snprintf(buf, sizeof(buf), "guestfwd.tcp.%d", port);
>> -    fwd->hd = qemu_chr_open(buf, p, NULL);
>> -    if (!fwd->hd) {
>> -        error_report("could not open guest forwarding device '%s'", buf);
>> -        qemu_free(fwd);
>> -        return -1;
>> -    }
>>
>> -    if (slirp_add_exec(s->slirp, 3, fwd->hd, &server, port) < 0) {
>> -        error_report("conflicting/invalid host:port in guest forwarding "
>> -                     "rule '%s'", config_str);
>> -        qemu_free(fwd);
>> -        return -1;
>> +    if ((strlen(p) > 4) && !strncmp(p, "cmd:", 4)) {
>> +        if (slirp_add_exec(s->slirp, 0, &p[4], &server, port) < 0) {
>> +            error_report("conflicting/invalid host:port in guest forwarding 
>> "
>> +                         "rule '%s'", config_str);
>> +            qemu_free(fwd);
>> +            return -1;
>> +        }
>> +    } else {
>> +        fwd->hd = qemu_chr_open(buf, p, NULL);
>> +        if (!fwd->hd) {
>> +            error_report("could not open guest forwarding device '%s'", 
>> buf);
>> +            qemu_free(fwd);
>> +            return -1;
>> +        }
>> +
>> +        if (slirp_add_exec(s->slirp, 3, fwd->hd, &server, port) < 0) {
>> +            error_report("conflicting/invalid host:port in guest forwarding 
>> "
>> +                         "rule '%s'", config_str);
>> +            qemu_free(fwd);
>> +            return -1;
>> +        }
>> +
>> +        fwd->server = server;
>> +        fwd->port = port;
>> +        fwd->slirp = s->slirp;
>> +
>> +        qemu_chr_add_handlers(fwd->hd, guestfwd_can_read, guestfwd_read,
>> +                              NULL, fwd);
>>     }
>> -    fwd->server = server;
>> -    fwd->port = port;
>> -    fwd->slirp = s->slirp;
>>
>> -    qemu_chr_add_handlers(fwd->hd, guestfwd_can_read, guestfwd_read,
>> -                          NULL, fwd);
>>     return 0;
>>
>>  fail_syntax:
>> diff --git a/qemu-options.hx b/qemu-options.hx
>> index 82e085a..cc62d20 100644
>> --- a/qemu-options.hx
>> +++ b/qemu-options.hx
>> @@ -1242,10 +1242,28 @@ telnet localhost 5555
>> Then when you use on the host @code{telnet localhost 5555}, you
>> connect to the guest telnet server.
>>
>> address@hidden guestfwd=[tcp]:@var{server}:@address@hidden
>> address@hidden guestfwd=[tcp]:@var{server}:@address@hidden|@var{cmd:command}]

This implies that the destination ("@var{dev}|@var{cmd:command}") is
optional. Probably it's clearer to express this with two lines.

>> Forward guest TCP connections to the IP address @var{server} on port 
>> @var{port}
>> to the character device @var{dev}. This option can be given multiple times.

Needs updating (only refers to the chardev variant).

>>
>> +You can either use a chardev directly and have that one used throughout 
>> Qemu's
>> +lifetime, like in the following example:
>> +
>> address@hidden
>> +# open 10.10.1.1:4321 on bootup, connect 10.0.2.100:1234 to it whenever
>> +# the guest accesses it
>> +qemu -net user,guestfwd=tcp:10.0.2.100:1234-tcp:10.10.1.1:4321 [...]
>> address@hidden example
>> +
>> +Or you can execute a command on every TCP connection established by the 
>> guest,
>> +so that Qemu behaves similar to an inetd process for that virtual server:
>> +
>> address@hidden
>> +# call "netcat 10.10.1.1 4321" on every TCP connection to 10.0.2.100:1234
>> +# and connect the TCP stream to its stdin/stdout
>> +qemu -net user,guestfwd=tcp:10.0.2.100:1234-cmd:netcat 10.10.1.1 4321

Must likely be ...-cmd:'netcat 10.10.1.1 4321'

>> address@hidden example
>> +
>> @end table
>>
>> Note: Legacy stand-alone options -tftp, -bootp, -smb and -redir are still
>> -- 
>> 1.6.0.2
>>
>>
> 

Jan

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