Connect stanza panics if network mode is not set to bridge

[nii236]

Nomad version

Nomad v0.10.0 (25ee121d951939504376c70bf8d7950c1ddb6a82)

Operating system and Environment details

Ubuntu 18.04

Issue

Server panics so the returned error message is not clear.

Example below is from the nomad/consul integration guide.

I understand the error message and what the problem is, I just wanted to report it as a panic is not desirable.

Reproduction steps

Working:

job "countdash" {
	datacenters = ["dc1"]
	group "api" {
		network {
			mode = "bridge"
		}

		service {
			name = "count-api"
			port = "9001"

			connect {
				sidecar_service {}
			}
		}
        ...
    }
}

Not working:

job "countdash" {
	datacenters = ["dc1"]
	group "api" {
		// network {
		// 	mode = "bridge"
		// }

		service {
			name = "count-api"
			port = "9001"

			connect {
				sidecar_service {}
			}
		}
        ...
    }
}

Job file (if appropriate)

Nomad Client logs (if appropriate)

$ nomad run count.nomad
Error submitting job: Put http://127.0.0.1:4646/v1/jobs: EOF

Nomad Server logs (if appropriate)

    2019/10/26 21:58:13.546974 http: panic serving 127.0.0.1:50794: runtime error: index out of range
goroutine 6408 [running]:
net/http.(*conn).serve.func1(0xc000de6500)
        /usr/local/go/src/net/http/server.go:1769 +0x139
panic(0x21e3d40, 0x42f6110)
        /usr/local/go/src/runtime/panic.go:522 +0x1b5
github.com/hashicorp/nomad/nomad.groupConnectHook(0xc000728ee0, 0x204c180, 0x48b48f)
        /opt/gopath/src/github.com/hashicorp/nomad/nomad/job_endpoint_hook_connect.go:127 +0x558
github.com/hashicorp/nomad/nomad.jobConnectHook.Mutate(0xc0009361e0, 0x16, 0xc000f62d70, 0xc000f62dd0, 0x200a7e0, 0xf80914, 0xf80745)
        /opt/gopath/src/github.com/hashicorp/nomad/nomad/job_endpoint_hook_connect.go:53 +0x71
github.com/hashicorp/nomad/nomad.(*Job).admissionMutators(0xc000502d70, 0xc0009361e0, 0xc000bc9ec0, 0x0, 0xc0005fe000, 0x7f67264ed6d0, 0x0, 0x451f38)
        /opt/gopath/src/github.com/hashicorp/nomad/nomad/job_endpoint_hooks.go:44 +0xd3
github.com/hashicorp/nomad/nomad.(*Job).admissionControllers(0xc000502d70, 0xc0009361e0, 0x7, 0x1, 0x3, 0xbf65321d609928bd, 0x2d2361d679, 0x4440640)
        /opt/gopath/src/github.com/hashicorp/nomad/nomad/job_endpoint_hooks.go:26 +0x4d
github.com/hashicorp/nomad/nomad.(*Job).Register(0xc000502d70, 0xc0014002a0, 0xc0004f54a0, 0x0, 0x0)
        /opt/gopath/src/github.com/hashicorp/nomad/nomad/job_endpoint.go:97 +0x3d4
reflect.Value.call(0xc0006b0780, 0xc000010c88, 0x13, 0x25ed51e, 0x4, 0xc000f63728, 0x3, 0x3, 0xc0004f54a0, 0x16, ...)
        /usr/local/go/src/reflect/value.go:447 +0x461
reflect.Value.Call(0xc0006b0780, 0xc000010c88, 0x13, 0xc000f63728, 0x3, 0x3, 0x16, 0x0, 0x241d980)
        /usr/local/go/src/reflect/value.go:308 +0xa4
net/rpc.(*service).call(0xc0003fa3c0, 0xc000502c30, 0xc001110e98, 0x0, 0xc00016e800, 0xc0004ccd00, 0x241d980, 0xc0014002a0, 0x16, 0x2299820, ...)
        /usr/local/go/src/net/rpc/server.go:384 +0x14e
net/rpc.(*Server).ServeRequest(0xc000502c30, 0x2a89ae0, 0xc0006bdcc0, 0xc000684000, 0xc0005fe000)
        /usr/local/go/src/net/rpc/server.go:505 +0x23e
github.com/hashicorp/nomad/nomad.(*Server).RPC(0xc000193340, 0x25fb9f0, 0xc, 0x241d980, 0xc001400240, 0x2299820, 0xc0004f5450, 0xc000e7e901, 0xc0004f5450)
        /opt/gopath/src/github.com/hashicorp/nomad/nomad/server.go:1441 +0xb9
github.com/hashicorp/nomad/command/agent.(*Agent).RPC(0xc00035c420, 0x25fb9f0, 0xc, 0x241d980, 0xc001400240, 0x2299820, 0xc0004f5450, 0x0, 0x8)
        /opt/gopath/src/github.com/hashicorp/nomad/command/agent/agent.go:919 +0x7a
github.com/hashicorp/nomad/command/agent.(*HTTPServer).jobUpdate(0xc000987310, 0x2a74c20, 0xc0014001e0, 0xc000e7e900, 0x0, 0x0, 0xc000773700, 0xc0013bf424, 0x8, 0x8)
        /opt/gopath/src/github.com/hashicorp/nomad/command/agent/job_endpoint.go:422 +0x386
github.com/hashicorp/nomad/command/agent.(*HTTPServer).JobsRequest(0xc000987310, 0x2a74c20, 0xc0014001e0, 0xc000e7e900, 0xc0004bb610, 0xc001608ac0, 0x38, 0xc001608ab8)
        /opt/gopath/src/github.com/hashicorp/nomad/command/agent/job_endpoint.go:21 +0x8a
github.com/hashicorp/nomad/command/agent.(*HTTPServer).wrap.func1(0x2a74c20, 0xc0014001e0, 0xc000e7e900)
        /opt/gopath/src/github.com/hashicorp/nomad/command/agent/http.go:294 +0x149
net/http.HandlerFunc.ServeHTTP(0xc000443d80, 0x2a74c20, 0xc0014001e0, 0xc000e7e900)
        /usr/local/go/src/net/http/server.go:1995 +0x44
net/http.(*ServeMux).ServeHTTP(0xc000773700, 0x2a74c20, 0xc0014001e0, 0xc000e7e900)
        /usr/local/go/src/net/http/server.go:2375 +0x1d6
github.com/hashicorp/nomad/vendor/github.com/NYTimes/gziphandler.GzipHandlerWithOpts.func1.1(0x2a77e20, 0xc000728b60, 0xc000e7e900)
        /opt/gopath/src/github.com/hashicorp/nomad/vendor/github.com/NYTimes/gziphandler/gzip.go:269 +0x1db
net/http.HandlerFunc.ServeHTTP(0xc000820180, 0x2a77e20, 0xc000728b60, 0xc000e7e900)
        /usr/local/go/src/net/http/server.go:1995 +0x44
net/http.serverHandler.ServeHTTP(0xc0006d8000, 0x2a77e20, 0xc000728b60, 0xc000e7e900)
        /usr/local/go/src/net/http/server.go:2774 +0xa8
net/http.(*conn).serve(0xc000de6500, 0x2a89820, 0xc0006bd780)
        /usr/local/go/src/net/http/server.go:1878 +0x851
created by net/http.(*Server).Serve
        /usr/local/go/src/net/http/server.go:2884 +0x2f4

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