absurdfarce opened a new issue, #1911:
URL: https://github.com/apache/cassandra-gocql-driver/issues/1911
Originally noted when this sample client:
```golang
package main
import (
"fmt"
gocql "github.com/apache/cassandra-gocql-driver/v2"
)
func main() {
cluster := gocql.NewCluster("127.0.0.1")
cluster.Logger = gocql.NewLogger(gocql.LogLevelDebug)
//cluster.ProtoVersion = 4
session, err := cluster.CreateSession()
if err != nil {
fmt.Println(err)
}
var dse_version string
query := session.Query(`select dse_version from
system.local`).Consistency(gocql.One)
if err = query.Scan(&dse_version); err != nil {
fmt.Println(err)
}
fmt.Println("Version is: ", dse_version)
}
```
built against
[v2.0.0-rc1](https://github.com/apache/cassandra-gocql-driver/tree/v2.0.0-rc1)
fails against DSE 6.9.0 with the following error:
```
$ ./version
2025/09/24 15:15:39 DBG gocql: Discovered protocol version using host.
protocol_version=5 host_addr=127.0.0.1 host_id=
2025/09/24 15:15:39 INF gocql: Discovered protocol version.
protocol_version=5
2025/09/24 15:15:39 WRN gocql: Control connection error. host_addr=127.0.0.1
host_id= err=gocql: crc24 mismatch in frame header, computed: 7052973, got: 0
2025/09/24 15:15:39 DBG gocql: Reconnecting the control connection.
2025/09/24 15:15:39 ERR gocql: Unable to connect to any ring node, control
connection falling back to initial contact points. err=
2025/09/24 15:15:39 INF gocql: Control connection setup failed after
connecting to host. host_addr=127.0.0.1 port=9042 host_id= err=could not
retrieve control host info: gocql: crc24 mismatch in frame header, computed:
7052973, got: 0
gocql: unable to create session: unable to connect to initial hosts: could
not retrieve control host info: gocql: crc24 mismatch in frame header,
computed: 7052973, got: 0
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x201c94]
goroutine 1 [running]:
github.com/apache/cassandra-gocql-driver/v2.(*Query).defaultsFromSession(...)
/home/mersault/go/pkg/mod/github.com/apache/cassandra-gocql-driver/[email protected]/session.go:1021
github.com/apache/cassandra-gocql-driver/v2.(*Session).Query(0x0, {0x2f772f,
0x24}, {0x0, 0x0, 0x0})
/home/mersault/go/pkg/mod/github.com/apache/cassandra-gocql-driver/[email protected]/session.go:436
+0x94
main.main()
/home/mersault/work/scratch/gocql-dse/version.go:20 +0x1ec
```
What's happening here is that the driver is trying to [use some
session-level values as defaults for the query
struct](https://github.com/apache/cassandra-gocql-driver/blob/v2.0.0-rc1/session.go#L1018-L1032)
and is failing to do so because those values are nil. Those values are nil
because the session setup never happens, and _that_ fails because we're trying
to apply protocol v5 frame decoding rules to a DSE server which (at best)
speaks protocol DSEv2.
This begs the question though... why did the client apply v5 framing rules
in this case? Clearly it did so because it detected protocol v5 was agreeable
to both parties (see the log messages in the snippet above)... but that's
clearly false. So what's going on here? The protocol detection logic (it's
not really a negotiation as such) lives
[here](https://github.com/apache/cassandra-gocql-driver/blob/v2.0.0-rc1/control.go#L226-L265).
When v5 support was added we wound up [modifying the session-level connection
config](https://github.com/apache/cassandra-gocql-driver/blob/v2.0.0-rc1/control.go#L230)
to v5 as part of the detection logic (and we don't reset it if detection
fails) which isn't great (since we're modifying session-level state in order to
try and perform detection) but that isn't the big problem.
Much more significant is the fact that we consider a protocol workable if
we're able to [dial the remote host without
errors](https://github.com/apache/cassandra-gocql-driver/blob/v2.0.0-rc1/control.go#L243-L252)
using that protocol version. The thing is that "dial the remote host" here
means establish a socket connection and exchange STARTUP messages (and
responses). And [according to the protocol v5
spec](https://github.com/apache/cassandra/blob/trunk/doc/native_protocol_v5.spec#L180-L185)
these messages are _always_ unframed. That means we'll always be able to
handle those responses for any server... and since we're starting with protocol
v5 we'll _always_ wind up returning v5 as the protocol version.
To confirm I tried the exact same code against Cassandra 3.11.9 which does
not support protocol v5. The results were basically the same:
```
$ ./version
2025/09/24 15:31:57 DBG gocql: Discovered protocol version using host.
protocol_version=5 host_addr=127.0.0.1 host_id=
2025/09/24 15:31:57 INF gocql: Discovered protocol version.
protocol_version=5
2025/09/24 15:31:57 WRN gocql: Control connection error. host_addr=127.0.0.1
host_id= err=gocql: crc24 mismatch in frame header, computed: 6994124, got: 0
2025/09/24 15:31:57 DBG gocql: Reconnecting the control connection.
2025/09/24 15:31:57 ERR gocql: Unable to connect to any ring node, control
connection falling back to initial contact points. err=
2025/09/24 15:31:57 INF gocql: Control connection setup failed after
connecting to host. host_addr=127.0.0.1 port=9042 host_id= err=could not
retrieve control host info: gocql: crc24 mismatch in frame header, computed:
6994124, got: 0
gocql: unable to create session: unable to connect to initial hosts: could
not retrieve control host info: gocql: crc24 mismatch in frame header,
computed: 6994124, got: 0
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x201c94]
goroutine 1 [running]:
github.com/apache/cassandra-gocql-driver/v2.(*Query).defaultsFromSession(...)
/home/mersault/go/pkg/mod/github.com/apache/cassandra-gocql-driver/[email protected]/session.go:1021
github.com/apache/cassandra-gocql-driver/v2.(*Session).Query(0x0, {0x2f772f,
0x24}, {0x0, 0x0, 0x0})
/home/mersault/go/pkg/mod/github.com/apache/cassandra-gocql-driver/[email protected]/session.go:436
+0x94
main.main()
/home/mersault/work/scratch/gocql-dse/version.go:20 +0x1ec
```
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