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Create new smux session for each SOCKS connection

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Each SOCKS connection has its own set of snowflakes and broker poll
loop. Since the session manager was tied to a single set of snowflakes,
this resulted in a bug where RedialPacketConn would sometimes try to
pull snowflakes from a previously melted pool. The fix is to maintain
separate smux sessions for each SOCKS connection, tied to its own
snowflake pool.
This commit is contained in:
Cecylia Bocovich 2020-11-23 14:02:54 -05:00
parent 5efcde5187
commit 114df695ce
1 changed files with 6 additions and 51 deletions
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57
client/lib/snowflake.go
View file

@ -6,7 +6,6 @@ import (
"io"
"log"
"net"
"sync"
"time"
"git.torproject.org/pluggable-transports/snowflake.git/common/turbotunnel"
@ -92,54 +91,6 @@ func newSession(snowflakes SnowflakeCollector) (net.PacketConn, *smux.Session, e
return pconn, sess, err
}
// sessionManager_ maintains a single global smux.Session that is shared among
// incoming SOCKS connections.
type sessionManager_ struct {
mutex sync.Mutex
sess *smux.Session
}
// Get creates and returns a new global smux.Session if none exists yet. If one
// already exists, it returns the existing one. It monitors the returned session
// and if it ever fails, sets things up so the next call to Get will create a
// new session.
func (manager *sessionManager_) Get(snowflakes SnowflakeCollector) (*smux.Session, error) {
manager.mutex.Lock()
defer manager.mutex.Unlock()
if manager.sess == nil {
log.Printf("starting a new session")
pconn, sess, err := newSession(snowflakes)
if err != nil {
return nil, err
}
manager.sess = sess
go func() {
// If the session dies, set it to be recreated.
for {
<-time.After(5 * time.Second)
if sess.IsClosed() {
break
}
}
log.Printf("discarding finished session")
// Close the underlying to force any ongoing WebRTC
// connection to close as well, and relinquish the
// SnowflakeCollector.
pconn.Close()
manager.mutex.Lock()
manager.sess = nil
manager.mutex.Unlock()
}()
} else {
log.Printf("reusing the existing session")
}
return manager.sess, nil
}
var sessionManager = sessionManager_{}
// Given an accepted SOCKS connection, establish a WebRTC connection to the
// remote peer and exchange traffic.
func Handler(socks net.Conn, tongue Tongue) error {
@ -155,8 +106,9 @@ func Handler(socks net.Conn, tongue Tongue) error {
log.Printf("---- Handler: begin collecting snowflakes ---")
go connectLoop(snowflakes)
// Return the global smux.Session.
sess, err := sessionManager.Get(snowflakes)
// Create a new smux session
log.Printf("---- Handler: starting a new session ---")
pconn, sess, err := newSession(snowflakes)
if err != nil {
return err
}
@ -174,6 +126,9 @@ func Handler(socks net.Conn, tongue Tongue) error {
log.Printf("---- Handler: closed stream %v ---", stream.ID())
snowflakes.End()
log.Printf("---- Handler: end collecting snowflakes ---")
pconn.Close()
sess.Close()
log.Printf("---- Handler: discarding finished session ---")
return nil
}