• Felix Lange's avatar
    p2p/discover: fix race involving the seed node iterator · b4374436
    Felix Lange authored
    nodeDB.querySeeds was not safe for concurrent use but could be called
    concurrenty on multiple goroutines in the following case:
    
    - the table was empty
    - a timed refresh started
    - a lookup was started and initiated refresh
    
    These conditions are unlikely to coincide during normal use, but are
    much more likely to occur all at once when the user's machine just woke
    from sleep. The root cause of the issue is that querySeeds reused the
    same leveldb iterator until it was exhausted.
    
    This commit moves the refresh scheduling logic into its own goroutine
    (so only one refresh is ever active) and changes querySeeds to not use
    a persistent iterator. The seed node selection is now more random and
    ignores nodes that have not been contacted in the last 5 days.
    b4374436
database.go 11.1 KB