| Message ID | 1339170179-2554-3-git-send-email-coreyb@linux.vnet.ibm.com |
|---|---|
| State | New |
| Headers | show |
On Fri, 8 Jun 2012 11:42:57 -0400 Corey Bryant <coreyb@linux.vnet.ibm.com> wrote: > This patch adds the passfd QMP command using the QAPI framework. > Like the getfd command, it is used to pass a file descriptor via > SCM_RIGHTS. However, the passfd command also returns the received > file descriptor, which is a difference in behavior from the getfd > command, which returns nothing. Let's call it pass-fd instead. Also, getfd automatically closes a fd if an existing fdname is passed again. I don't think this is a good behavior, I think pass-fd should fail instead (note that we can't fix getfd though). > > The closefd command can be used to close a file descriptor that was > passed with the passfd command. > > v2: > -Introduce new QMP command to pass/return fd (lcapitulino@redhat.com) > -Use passfd as command name (berrange@redhat.com) > > Signed-off-by: Corey Bryant <coreyb@linux.vnet.ibm.com> > --- > monitor.c | 14 ++++++++++---- > qapi-schema.json | 15 +++++++++++++++ > qmp-commands.hx | 27 +++++++++++++++++++++++++++ > 3 files changed, 52 insertions(+), 4 deletions(-) > > diff --git a/monitor.c b/monitor.c > index 4c53cb6..980a226 100644 > --- a/monitor.c > +++ b/monitor.c > @@ -2182,7 +2182,7 @@ static void do_inject_mce(Monitor *mon, const QDict *qdict) > } > #endif > > -void qmp_getfd(const char *fdname, Error **errp) > +int64_t qmp_passfd(const char *fdname, Error **errp) > { > mon_fd_t *monfd; > int fd; > @@ -2190,13 +2190,13 @@ void qmp_getfd(const char *fdname, Error **errp) > fd = qemu_chr_fe_get_msgfd(cur_mon->chr); > if (fd == -1) { > error_set(errp, QERR_FD_NOT_SUPPLIED); > - return; > + return -1; > } > > if (qemu_isdigit(fdname[0])) { > error_set(errp, QERR_INVALID_PARAMETER_VALUE, "fdname", > "a name not starting with a digit"); > - return; > + return -1; > } > > QLIST_FOREACH(monfd, &cur_mon->fds, next) { > @@ -2206,7 +2206,7 @@ void qmp_getfd(const char *fdname, Error **errp) > > close(monfd->fd); > monfd->fd = fd; > - return; > + return fd; > } > > monfd = g_malloc0(sizeof(mon_fd_t)); > @@ -2214,6 +2214,12 @@ void qmp_getfd(const char *fdname, Error **errp) > monfd->fd = fd; > > QLIST_INSERT_HEAD(&cur_mon->fds, monfd, next); > + return fd; > +} > + > +void qmp_getfd(const char *fdname, Error **errp) > +{ > + qmp_passfd(fdname, errp); > return; > } > > diff --git a/qapi-schema.json b/qapi-schema.json > index 6be1d90..15da1b8 100644 > --- a/qapi-schema.json > +++ b/qapi-schema.json > @@ -1864,6 +1864,21 @@ > { 'command': 'netdev_del', 'data': {'id': 'str'} } > > ## > +# @passfd: > +# > +# Pass a file descriptor via SCM rights and assign it a name > +# > +# @fdname: file descriptor name > +# > +# Returns: The QEMU file descriptor that was received > +# If file descriptor was not received, FdNotSupplied > +# If @fdname is not valid, InvalidParameterType > +# > +# Since: 1.2.0 > +## > +{ 'command': 'passfd', 'data': {'fdname': 'str'}, 'returns': 'int' } > + > +## > # @getfd: > # > # Receive a file descriptor via SCM rights and assign it a name > diff --git a/qmp-commands.hx b/qmp-commands.hx > index f8c0f68..338a0b3 100644 > --- a/qmp-commands.hx > +++ b/qmp-commands.hx > @@ -869,6 +869,33 @@ Example: > EQMP > > { > + .name = "passfd", > + .args_type = "fdname:s", > + .params = "passfd name", > + .help = "pass a file descriptor via SCM rights and assign it a name", > + .mhandler.cmd_new = qmp_marshal_input_passfd, > + }, > + > +SQMP > +passfd > +------ > + > +Pass a file descriptor via SCM rights and assign it a name. > + > +Arguments: > + > +- "fdname": file descriptor name (json-string) > + > +Return a json-int with the QEMU file descriptor that was received. > + > +Example: > + > +-> { "execute": "passfd", "arguments": { "fdname": "fd1" } } > +<- { "return": 42 } > + > +EQMP > + > + { > .name = "getfd", > .args_type = "fdname:s", > .params = "getfd name",
On 06/13/2012 03:46 PM, Luiz Capitulino wrote: > On Fri, 8 Jun 2012 11:42:57 -0400 > Corey Bryant <coreyb@linux.vnet.ibm.com> wrote: > >> This patch adds the passfd QMP command using the QAPI framework. >> Like the getfd command, it is used to pass a file descriptor via >> SCM_RIGHTS. However, the passfd command also returns the received >> file descriptor, which is a difference in behavior from the getfd >> command, which returns nothing. > > Let's call it pass-fd instead. Sure, that works for me. > > Also, getfd automatically closes a fd if an existing fdname is passed again. > I don't think this is a good behavior, I think pass-fd should fail instead > (note that we can't fix getfd though). > I agree. It makes sense to fail rather than blindly closing the existing fd. It can be closed explicitly with closefd if the user wants it closed. >> >> The closefd command can be used to close a file descriptor that was >> passed with the passfd command. >> >> v2: >> -Introduce new QMP command to pass/return fd (lcapitulino@redhat.com) >> -Use passfd as command name (berrange@redhat.com) >> >> Signed-off-by: Corey Bryant <coreyb@linux.vnet.ibm.com> >> --- >> monitor.c | 14 ++++++++++---- >> qapi-schema.json | 15 +++++++++++++++ >> qmp-commands.hx | 27 +++++++++++++++++++++++++++ >> 3 files changed, 52 insertions(+), 4 deletions(-) >> >> diff --git a/monitor.c b/monitor.c >> index 4c53cb6..980a226 100644 >> --- a/monitor.c >> +++ b/monitor.c >> @@ -2182,7 +2182,7 @@ static void do_inject_mce(Monitor *mon, const QDict *qdict) >> } >> #endif >> >> -void qmp_getfd(const char *fdname, Error **errp) >> +int64_t qmp_passfd(const char *fdname, Error **errp) >> { >> mon_fd_t *monfd; >> int fd; >> @@ -2190,13 +2190,13 @@ void qmp_getfd(const char *fdname, Error **errp) >> fd = qemu_chr_fe_get_msgfd(cur_mon->chr); >> if (fd == -1) { >> error_set(errp, QERR_FD_NOT_SUPPLIED); >> - return; >> + return -1; >> } >> >> if (qemu_isdigit(fdname[0])) { >> error_set(errp, QERR_INVALID_PARAMETER_VALUE, "fdname", >> "a name not starting with a digit"); >> - return; >> + return -1; >> } >> >> QLIST_FOREACH(monfd, &cur_mon->fds, next) { >> @@ -2206,7 +2206,7 @@ void qmp_getfd(const char *fdname, Error **errp) >> >> close(monfd->fd); >> monfd->fd = fd; >> - return; >> + return fd; >> } >> >> monfd = g_malloc0(sizeof(mon_fd_t)); >> @@ -2214,6 +2214,12 @@ void qmp_getfd(const char *fdname, Error **errp) >> monfd->fd = fd; >> >> QLIST_INSERT_HEAD(&cur_mon->fds, monfd, next); >> + return fd; >> +} >> + >> +void qmp_getfd(const char *fdname, Error **errp) >> +{ >> + qmp_passfd(fdname, errp); >> return; >> } >> >> diff --git a/qapi-schema.json b/qapi-schema.json >> index 6be1d90..15da1b8 100644 >> --- a/qapi-schema.json >> +++ b/qapi-schema.json >> @@ -1864,6 +1864,21 @@ >> { 'command': 'netdev_del', 'data': {'id': 'str'} } >> >> ## >> +# @passfd: >> +# >> +# Pass a file descriptor via SCM rights and assign it a name >> +# >> +# @fdname: file descriptor name >> +# >> +# Returns: The QEMU file descriptor that was received >> +# If file descriptor was not received, FdNotSupplied >> +# If @fdname is not valid, InvalidParameterType >> +# >> +# Since: 1.2.0 >> +## >> +{ 'command': 'passfd', 'data': {'fdname': 'str'}, 'returns': 'int' } >> + >> +## >> # @getfd: >> # >> # Receive a file descriptor via SCM rights and assign it a name >> diff --git a/qmp-commands.hx b/qmp-commands.hx >> index f8c0f68..338a0b3 100644 >> --- a/qmp-commands.hx >> +++ b/qmp-commands.hx >> @@ -869,6 +869,33 @@ Example: >> EQMP >> >> { >> + .name = "passfd", >> + .args_type = "fdname:s", >> + .params = "passfd name", >> + .help = "pass a file descriptor via SCM rights and assign it a name", >> + .mhandler.cmd_new = qmp_marshal_input_passfd, >> + }, >> + >> +SQMP >> +passfd >> +------ >> + >> +Pass a file descriptor via SCM rights and assign it a name. >> + >> +Arguments: >> + >> +- "fdname": file descriptor name (json-string) >> + >> +Return a json-int with the QEMU file descriptor that was received. >> + >> +Example: >> + >> +-> { "execute": "passfd", "arguments": { "fdname": "fd1" } } >> +<- { "return": 42 } >> + >> +EQMP >> + >> + { >> .name = "getfd", >> .args_type = "fdname:s", >> .params = "getfd name", >
On 06/13/2012 02:25 PM, Corey Bryant wrote: >> Also, getfd automatically closes a fd if an existing fdname is passed >> again. >> I don't think this is a good behavior, I think pass-fd should fail >> instead >> (note that we can't fix getfd though). >> > > I agree. It makes sense to fail rather than blindly closing the > existing fd. It can be closed explicitly with closefd if the user wants > it closed. Hmm - what happens if I do 'pass-fd name', learn that qemu is using fd 42, then do 'getfd name'? I silently wipe out fd 42 and replace it with the new fd passed in by getfd. Which means my use of /dev/fd/42 will now be broken. Obviously that means that 'getfd' should NOT be used by any application using 'pass-fd', and that libvirt should NOT be reusing names (I think the latter is already true). But I agree that for back-compat we can't get rid of the current (evil) semantics of a duplicated 'getfd'. You may also want to mention that when using 'getfd' or 'pass-fd', there are some commands (like migrate) that use the fd:name protocol, and that a successful use of one of these commands implicitly closes the named fd; but that all new uses of /dev/fd/nnn leave the fd open and an explicit closefd must be used to avoid leaking indefinitely-opened fds in qemu.
On 06/13/2012 04:47 PM, Eric Blake wrote: > On 06/13/2012 02:25 PM, Corey Bryant wrote: > >>> Also, getfd automatically closes a fd if an existing fdname is passed >>> again. >>> I don't think this is a good behavior, I think pass-fd should fail >>> instead >>> (note that we can't fix getfd though). >>> >> >> I agree. It makes sense to fail rather than blindly closing the >> existing fd. It can be closed explicitly with closefd if the user wants >> it closed. > > Hmm - what happens if I do 'pass-fd name', learn that qemu is using fd > 42, then do 'getfd name'? I silently wipe out fd 42 and replace it with > the new fd passed in by getfd. Which means my use of /dev/fd/42 will > now be broken. > > Obviously that means that 'getfd' should NOT be used by any application > using 'pass-fd', and that libvirt should NOT be reusing names (I think > the latter is already true). But I agree that for back-compat we can't > get rid of the current (evil) semantics of a duplicated 'getfd'. Yes, users need to be careful and understand how the commands work. I don't think it's a hard rule that 'getfd' can't be used by an application that uses 'pass-fd'. If it were, we could put the fds on separate lists: struct Monitor { ... QLIST_HEAD(,mon_fd_t) fds; + QLIST_HEAD(,mon_fd_t) pass_fds; }; But I don't think this is necessary, so I'll plan on documenting them well. > > You may also want to mention that when using 'getfd' or 'pass-fd', there > are some commands (like migrate) that use the fd:name protocol, and that > a successful use of one of these commands implicitly closes the named > fd; but that all new uses of /dev/fd/nnn leave the fd open and an > explicit closefd must be used to avoid leaking indefinitely-opened fds > in qemu. > Ok, I'll mention this too. Thanks.
On Wed, 13 Jun 2012 18:07:43 -0400 Corey Bryant <coreyb@linux.vnet.ibm.com> wrote: > > > On 06/13/2012 04:47 PM, Eric Blake wrote: > > On 06/13/2012 02:25 PM, Corey Bryant wrote: > > > >>> Also, getfd automatically closes a fd if an existing fdname is passed > >>> again. > >>> I don't think this is a good behavior, I think pass-fd should fail > >>> instead > >>> (note that we can't fix getfd though). > >>> > >> > >> I agree. It makes sense to fail rather than blindly closing the > >> existing fd. It can be closed explicitly with closefd if the user wants > >> it closed. > > > > Hmm - what happens if I do 'pass-fd name', learn that qemu is using fd > > 42, then do 'getfd name'? I silently wipe out fd 42 and replace it with > > the new fd passed in by getfd. Which means my use of /dev/fd/42 will > > now be broken. > > > > Obviously that means that 'getfd' should NOT be used by any application > > using 'pass-fd', and that libvirt should NOT be reusing names (I think > > the latter is already true). But I agree that for back-compat we can't > > get rid of the current (evil) semantics of a duplicated 'getfd'. > > Yes, users need to be careful and understand how the commands work. I > don't think it's a hard rule that 'getfd' can't be used by an > application that uses 'pass-fd'. If it were, we could put the fds on > separate lists: > > struct Monitor { > ... > QLIST_HEAD(,mon_fd_t) fds; > + QLIST_HEAD(,mon_fd_t) pass_fds; > }; We'd a different closefd command if we do this. > But I don't think this is necessary, so I'll plan on documenting them well. Agreed, I don't think this is necessary.
diff --git a/monitor.c b/monitor.c index 4c53cb6..980a226 100644 --- a/monitor.c +++ b/monitor.c @@ -2182,7 +2182,7 @@ static void do_inject_mce(Monitor *mon, const QDict *qdict) } #endif -void qmp_getfd(const char *fdname, Error **errp) +int64_t qmp_passfd(const char *fdname, Error **errp) { mon_fd_t *monfd; int fd; @@ -2190,13 +2190,13 @@ void qmp_getfd(const char *fdname, Error **errp) fd = qemu_chr_fe_get_msgfd(cur_mon->chr); if (fd == -1) { error_set(errp, QERR_FD_NOT_SUPPLIED); - return; + return -1; } if (qemu_isdigit(fdname[0])) { error_set(errp, QERR_INVALID_PARAMETER_VALUE, "fdname", "a name not starting with a digit"); - return; + return -1; } QLIST_FOREACH(monfd, &cur_mon->fds, next) { @@ -2206,7 +2206,7 @@ void qmp_getfd(const char *fdname, Error **errp) close(monfd->fd); monfd->fd = fd; - return; + return fd; } monfd = g_malloc0(sizeof(mon_fd_t)); @@ -2214,6 +2214,12 @@ void qmp_getfd(const char *fdname, Error **errp) monfd->fd = fd; QLIST_INSERT_HEAD(&cur_mon->fds, monfd, next); + return fd; +} + +void qmp_getfd(const char *fdname, Error **errp) +{ + qmp_passfd(fdname, errp); return; } diff --git a/qapi-schema.json b/qapi-schema.json index 6be1d90..15da1b8 100644 --- a/qapi-schema.json +++ b/qapi-schema.json @@ -1864,6 +1864,21 @@ { 'command': 'netdev_del', 'data': {'id': 'str'} } ## +# @passfd: +# +# Pass a file descriptor via SCM rights and assign it a name +# +# @fdname: file descriptor name +# +# Returns: The QEMU file descriptor that was received +# If file descriptor was not received, FdNotSupplied +# If @fdname is not valid, InvalidParameterType +# +# Since: 1.2.0 +## +{ 'command': 'passfd', 'data': {'fdname': 'str'}, 'returns': 'int' } + +## # @getfd: # # Receive a file descriptor via SCM rights and assign it a name diff --git a/qmp-commands.hx b/qmp-commands.hx index f8c0f68..338a0b3 100644 --- a/qmp-commands.hx +++ b/qmp-commands.hx @@ -869,6 +869,33 @@ Example: EQMP { + .name = "passfd", + .args_type = "fdname:s", + .params = "passfd name", + .help = "pass a file descriptor via SCM rights and assign it a name", + .mhandler.cmd_new = qmp_marshal_input_passfd, + }, + +SQMP +passfd +------ + +Pass a file descriptor via SCM rights and assign it a name. + +Arguments: + +- "fdname": file descriptor name (json-string) + +Return a json-int with the QEMU file descriptor that was received. + +Example: + +-> { "execute": "passfd", "arguments": { "fdname": "fd1" } } +<- { "return": 42 } + +EQMP + + { .name = "getfd", .args_type = "fdname:s", .params = "getfd name",
This patch adds the passfd QMP command using the QAPI framework. Like the getfd command, it is used to pass a file descriptor via SCM_RIGHTS. However, the passfd command also returns the received file descriptor, which is a difference in behavior from the getfd command, which returns nothing. The closefd command can be used to close a file descriptor that was passed with the passfd command. v2: -Introduce new QMP command to pass/return fd (lcapitulino@redhat.com) -Use passfd as command name (berrange@redhat.com) Signed-off-by: Corey Bryant <coreyb@linux.vnet.ibm.com> --- monitor.c | 14 ++++++++++---- qapi-schema.json | 15 +++++++++++++++ qmp-commands.hx | 27 +++++++++++++++++++++++++++ 3 files changed, 52 insertions(+), 4 deletions(-)