Fixed findings:
```
lib/sshutils/server_test.go:163:2: SA4006: this value of `clt` is never used (staticcheck)
clt, err := ssh.Dial("tcp", srv.Addr(), &cc)
^
lib/sshutils/server_test.go:91:3: SA5001: should check returned error before deferring ch.Close() (staticcheck)
defer ch.Close()
^
lib/shell/shell_test.go:33:2: SA4006: this value of `shell` is never used (staticcheck)
shell, err = GetLoginShell("non-existent-user")
^
lib/cgroup/cgroup_test.go:111:2: SA9003: empty branch (staticcheck)
if err != nil {
^
lib/cgroup/cgroup_test.go:119:2: SA5001: should check returned error before deferring service.Close() (staticcheck)
defer service.Close()
^
lib/client/keystore_test.go:138:2: SA4006: this value of `keyCopy` is never used (staticcheck)
keyCopy, err = s.store.GetKey("host.a", "bob")
^
lib/client/api.go:1604:3: SA4004: the surrounding loop is unconditionally terminated (staticcheck)
return makeProxyClient(sshClient, m), nil
^
lib/backend/test/suite.go:156:2: SA4006: this value of `err` is never used (staticcheck)
result, err = s.B.GetRange(ctx, prefix("/prefix/c/c1"), backend.RangeEnd(prefix("/prefix/c/cz")), backend.NoLimit)
^
lib/utils/timeout_test.go:84:2: SA1019: t.Dial is deprecated: Use DialContext instead, which allows the transport to cancel dials as soon as they are no longer needed. If both are set, DialContext takes priority. (staticcheck)
t.Dial = func(network string, addr string) (net.Conn, error) {
^
lib/utils/websocketwriter.go:83:3: SA4006: this value of `err` is never used (staticcheck)
utf8, err = w.encoder.String(string(data))
^
lib/utils/loadbalancer_test.go:134:2: SA4006: this value of `out` is never used (staticcheck)
out, err = Roundtrip(frontend.String())
^
lib/utils/loadbalancer_test.go:209:2: SA4006: this value of `out` is never used (staticcheck)
out, err = RoundtripWithConn(conn)
^
lib/srv/forward/sshserver.go:582:3: SA4004: the surrounding loop is unconditionally terminated (staticcheck)
return
^
lib/service/service.go:347:4: SA4006: this value of `err` is never used (staticcheck)
i, err = auth.GenerateIdentity(process.localAuth, id, principals, dnsNames)
^
lib/service/signals.go:60:3: SA1016: syscall.SIGKILL cannot be trapped (did you mean syscall.SIGTERM?) (staticcheck)
syscall.SIGKILL, // fast shutdown
^
lib/config/configuration_test.go:184:2: SA4006: this value of `conf` is never used (staticcheck)
conf, err = ReadFromFile(s.configFileBadContent)
^
lib/config/configuration.go:129:2: SA5001: should check returned error before deferring reader.Close() (staticcheck)
defer reader.Close()
^
lib/kube/kubeconfig/kubeconfig_test.go:227:2: SA4006: this value of `err` is never used (staticcheck)
tlsCert, err := ca.GenerateCertificate(tlsca.CertificateRequest{
^
lib/srv/sess.go:720:3: SA4006: this value of `err` is never used (staticcheck)
result, err := s.term.Wait()
^
lib/multiplexer/multiplexer_test.go:169:11: SA1006: printf-style function with dynamic format string and no further arguments should use print-style function instead (staticcheck)
_, err = fmt.Fprintf(conn, proxyLine.String())
^
lib/multiplexer/multiplexer_test.go:221:11: SA1006: printf-style function with dynamic format string and no further arguments should use print-style function instead (staticcheck)
_, err = fmt.Fprintf(conn, proxyLine.String())
^
```
All changes should be noop, except for
`integration/integration_test.go`.
The integration test was ignoring `recordingMode` test case parameter
and always used `RecordAtNode`. When switching to `recordingMode`, test
cases with `RecordAtProxy` fail with a confusing error about missing
user agent. Filed https://github.com/gravitational/teleport/issues/3606
to track that separately and unblock enabling `structcheck` linter.
Spring cleaning!
A very mechanical cleanup using several linters (unused, deadcode,
structcheck). Build and tests still pass so no behavior should be
affected.
This was fixed running the `misspell` linter in fix mode using
`gometalinter`. The exact command I ran was :
```
gometalinter --vendor --disable-all -E misspell --linter='misspell:misspell -w {path}:^(?P<path>.*?\.go):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.*)$' ./...
```
Some typo were fixed by hand on top of it.
- Added idle timeout handling to every SSH connection.
- A bit of code refactoring (removing unused code paths)
Most importantly:
Added a custom SSH handshake between SSH Teleport proxies
and SSH Teleport servers. This handshake sends a custom JSON payload
from a proxy to a server, allowing to exchange additional information,
like the true IP of a client.
fheinecke