github.com/decred/dcrlnd@v0.7.6/chanacceptor/chainedacceptor.go (about)

     1  package chanacceptor
     2  
     3  import (
     4  	"sync"
     5  	"sync/atomic"
     6  )
     7  
     8  // ChainedAcceptor represents a conjunction of ChannelAcceptor results.
     9  type ChainedAcceptor struct {
    10  	acceptorID uint64 // To be used atomically.
    11  
    12  	// acceptors is a map of ChannelAcceptors that will be evaluated when
    13  	// the ChainedAcceptor's Accept method is called.
    14  	acceptors    map[uint64]ChannelAcceptor
    15  	acceptorsMtx sync.RWMutex
    16  }
    17  
    18  // NewChainedAcceptor initializes a ChainedAcceptor.
    19  func NewChainedAcceptor() *ChainedAcceptor {
    20  	return &ChainedAcceptor{
    21  		acceptors: make(map[uint64]ChannelAcceptor),
    22  	}
    23  }
    24  
    25  // AddAcceptor adds a ChannelAcceptor to this ChainedAcceptor.
    26  func (c *ChainedAcceptor) AddAcceptor(acceptor ChannelAcceptor) uint64 {
    27  	id := atomic.AddUint64(&c.acceptorID, 1)
    28  
    29  	c.acceptorsMtx.Lock()
    30  	c.acceptors[id] = acceptor
    31  	c.acceptorsMtx.Unlock()
    32  
    33  	// Return the id so that a caller can call RemoveAcceptor.
    34  	return id
    35  }
    36  
    37  // RemoveAcceptor removes a ChannelAcceptor from this ChainedAcceptor given
    38  // an ID.
    39  func (c *ChainedAcceptor) RemoveAcceptor(id uint64) {
    40  	c.acceptorsMtx.Lock()
    41  	delete(c.acceptors, id)
    42  	c.acceptorsMtx.Unlock()
    43  }
    44  
    45  // Accept evaluates the results of all ChannelAcceptors in the acceptors map
    46  // and returns the conjunction of all these predicates.
    47  //
    48  // NOTE: Part of the ChannelAcceptor interface.
    49  func (c *ChainedAcceptor) Accept(req *ChannelAcceptRequest) *ChannelAcceptResponse {
    50  	c.acceptorsMtx.RLock()
    51  	defer c.acceptorsMtx.RUnlock()
    52  
    53  	var finalResp ChannelAcceptResponse
    54  
    55  	for _, acceptor := range c.acceptors {
    56  		// Call our acceptor to determine whether we want to accept this
    57  		// channel.
    58  		acceptorResponse := acceptor.Accept(req)
    59  
    60  		// If we should reject the channel, we can just exit early. This
    61  		// has the effect of returning the error belonging to our first
    62  		// failed acceptor.
    63  		if acceptorResponse.RejectChannel() {
    64  			return acceptorResponse
    65  		}
    66  
    67  		// If we have accepted the channel, we need to set the other
    68  		// fields that were set in the response. However, since we are
    69  		// dealing with multiple responses, we need to make sure that we
    70  		// have not received inconsistent values (eg a csv delay of 1
    71  		// from one acceptor, and a delay of 120 from another). We
    72  		// set each value on our final response if it has not been set
    73  		// yet, and allow duplicate sets if the value is the same. If
    74  		// we cannot set a field, we return an error response.
    75  		var err error
    76  		finalResp, err = mergeResponse(finalResp, *acceptorResponse)
    77  		if err != nil {
    78  			log.Errorf("response for: %x has inconsistent values: %v",
    79  				req.OpenChanMsg.PendingChannelID, err)
    80  
    81  			return NewChannelAcceptResponse(
    82  				false, errChannelRejected, nil, 0, 0,
    83  				0, 0, 0, 0,
    84  			)
    85  		}
    86  	}
    87  
    88  	// If we have gone through all of our acceptors with no objections, we
    89  	// can return an acceptor with a nil error.
    90  	return &finalResp
    91  }
    92  
    93  // A compile-time constraint to ensure ChainedAcceptor implements the
    94  // ChannelAcceptor interface.
    95  var _ ChannelAcceptor = (*ChainedAcceptor)(nil)