Duplicated network setup for stacks

[yomimono]

For unikernels that request a stack (like the network example in mirage-skeleton), Mirage currently generates a main.ml that duplicates connection code many times over and results in a stack built with distinct (but identically configured) records for the underlying implementations. For example, here's the snippet that generates the tcp and udp records, from a main.ml made with mirage configure --xen in the aforementioned example:

let udp1 () =                                                                   
  let __ipv411 = ipv411 () in                                                   
  __ipv411 >>= function                                                         
  | `Error _e -> fail (Failure "ipv411")                                        
  | `Ok _ipv411 ->                                                              
  Udp1.connect _ipv411                                                          

let tcp1 () =                                                                   
  let __ipv411 = ipv411 () in                                                   
  let __time1 = time1 () in                                                     
  let __clock1 = clock1 () in                                                   
  let __random1 = random1 () in                                                 
  __ipv411 >>= function                                                         
  | `Error _e -> fail (Failure "ipv411")                                        
  | `Ok _ipv411 ->                                                              
  __time1 >>= function                                                          
  | `Error _e -> fail (Failure "time1")                                         
  | `Ok _time1 ->                                                               
  __clock1 >>= function                                                         
  | `Error _e -> fail (Failure "clock1")                                        
  | `Ok _clock1 ->                                                              
  __random1 >>= function                                                        
  | `Error _e -> fail (Failure "random1")                                       
  | `Ok _random1 ->                                                             
  Tcp1.connect _ipv411                           

Each calls ipv411 (), which results in a new ip record. ipv411 () itself generates new underlying records each time it's called, resulting in output like the following when the unikernel starts up:

Netif: add resume hook
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netif.connect 0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
Netfront.create: id=0 domid=0
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce
MAC: 00:16:3e:13:06:ce

Functions like tcp1 and udp1 should probably take the required subcomponents as arguments, rather than generating them within the function and not exposing them.

[Drup]

Functions like tcp1 and udp1 should probably take the required subcomponents as arguments, rather than generating them within the function and not exposing them.

Alternatively, instead of a unit function, we return a Lazy, this should solve the problem once and for all.

[yomimono]

Would you not still have the problem of distinct records (rather than everything being built on top of the same netif/ethif/ip/arp/etc record) with the lazy approach?

[Drup]

I don't think so. The udp example would look like that :

let udp1 = lazy (
  let __ipv411 = Lazy.force ipv411 in                                                   
  __ipv411 >>= function                                                         
  | `Error _e -> fail (Failure "ipv411")                                        
  | `Ok _ipv411 ->                                                              
  Udp1.connect _ipv411)

[yallop]

This appears to have been fixed by mirage/functoria#44. @yomimono, can you confirm?

[yomimono]

Yes, all appears to be well now; closing.