Re: why is it not allowed to add a new socket protocol family as an external module?

[Eric Dumazet <eric.dumazet@gmail.com>]

On Thu, 2013-02-21 at 09:47 -0600, Chris Friesen wrote:
> On 02/20/2013 07:39 PM, Eric Dumazet wrote:
> > On Wed, 2013-02-20 at 18:44 -0600, Chris Friesen wrote:
> >
> >> Yes, there are a number of tables sized by NPROTO/AF_MAX/PF_MAX (and the
> >> fact that we use all three within the kernel is kind of sad) but there
> >> is no technical reason why we couldn't extend those dynamically if
> >> desired (with a linked list of additional protocols, perhaps).
> >>
> >> Hence my question--is the restriction for an ideological reason or
> >> simply because nobody thought it was worth the effort?
> >>
> >
> > I guess nobody did the preliminary work.
> >
> > lockdep might be the tricky part.
> >
> > net/core/sock.c:197:static const char *const af_family_key_strings[AF_MAX+1] = {
> > net/core/sock.c:211:  "sk_lock-AF_NFC"   , "sk_lock-AF_MAX"
> > net/core/sock.c:213:static const char *const af_family_slock_key_strings[AF_MAX+1] = {
> > net/core/sock.c:227:  "slock-AF_NFC"   , "slock-AF_MAX"
> > net/core/sock.c:229:static const char *const af_family_clock_key_strings[AF_MAX+1] = {
> > net/core/sock.c:243:  "clock-AF_NFC"   , "clock-AF_MAX"
> > net/core/sock.c:250:static struct lock_class_key af_callback_keys[AF_MAX];
> 
> Unless I'm missing something that looks straightforward.
> 
> When registering dynamically the new protocol would need to specify one 
> string, the protocol name.  ("AF_MYPROTOCOL" or something).  The three 
> key strings are derived from that.
> 
> The three lock_class_key structs (corresponding to 
> af_family_keys/af_family_slock_keys/af_callback_keys) can be 
> auto-allocated by the network core at dynamic registration time.

Nope, this was the point I specifically raised but you missed it

Take a look at kernel/lockdep.c, lines 2981-2988

All the other stuff you mention seems pretty obvious.