From 3b4bb947517d0d9010120aaa1c3989fd6abf278e Mon Sep 17 00:00:00 2001 From: Ghanan Gowripalan Date: Thu, 19 Aug 2021 13:51:40 -0700 Subject: Add loopback interface as an ethernet-based device ...to match Linux behaviour. We can see evidence of Linux representing loopback as an ethernet-based device below: ``` # EUI-48 based MAC addresses. $ ip link show lo 1: lo: mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 # tcpdump showing ethernet frames when sniffing loopback and logging the # link-type as EN10MB (Ethernet). $ sudo tcpdump -i lo -e -c 2 -n tcpdump: verbose output suppressed, use -v[v]... for full protocol decode listening on lo, link-type EN10MB (Ethernet), snapshot length 262144 bytes 03:09:05.002034 00:00:00:00:00:00 > 00:00:00:00:00:00, ethertype IPv4 (0x0800), length 66: 127.0.0.1.9557 > 127.0.0.1.36828: Flags [.], ack 3562800815, win 15342, options [nop,nop,TS val 843174495 ecr 843159493], length 0 03:09:05.002094 00:00:00:00:00:00 > 00:00:00:00:00:00, ethertype IPv4 (0x0800), length 66: 127.0.0.1.36828 > 127.0.0.1.9557: Flags [.], ack 1, win 6160, options [nop,nop,TS val 843174496 ecr 843159493], length 0 2 packets captured 116 packets received by filter 0 packets dropped by kernel ``` Wireshark shows a similar result as the tcpdump example above. Linux's loopback setup: https://github.com/torvalds/linux/blob/5bfc75d92efd494db37f5c4c173d3639d4772966/drivers/net/loopback.c#L162 PiperOrigin-RevId: 391836719 --- runsc/boot/BUILD | 1 + runsc/boot/loader.go | 3 ++- runsc/boot/network.go | 3 ++- 3 files changed, 5 insertions(+), 2 deletions(-) (limited to 'runsc') diff --git a/runsc/boot/BUILD b/runsc/boot/BUILD index 1c57f9dd5..0ded907f0 100644 --- a/runsc/boot/BUILD +++ b/runsc/boot/BUILD @@ -97,6 +97,7 @@ go_library( "//pkg/sentry/watchdog", "//pkg/sync", "//pkg/tcpip", + "//pkg/tcpip/link/ethernet", "//pkg/tcpip/link/fdbased", "//pkg/tcpip/link/loopback", "//pkg/tcpip/link/packetsocket", diff --git a/runsc/boot/loader.go b/runsc/boot/loader.go index ec9188021..3f667cd74 100644 --- a/runsc/boot/loader.go +++ b/runsc/boot/loader.go @@ -58,6 +58,7 @@ import ( "gvisor.dev/gvisor/pkg/sentry/watchdog" "gvisor.dev/gvisor/pkg/sync" "gvisor.dev/gvisor/pkg/tcpip" + "gvisor.dev/gvisor/pkg/tcpip/link/ethernet" "gvisor.dev/gvisor/pkg/tcpip/link/loopback" "gvisor.dev/gvisor/pkg/tcpip/link/sniffer" "gvisor.dev/gvisor/pkg/tcpip/network/arp" @@ -1174,7 +1175,7 @@ func (f *sandboxNetstackCreator) CreateStack() (inet.Stack, error) { n := &Network{Stack: s.(*netstack.Stack).Stack} nicID := tcpip.NICID(f.uniqueID.UniqueID()) link := DefaultLoopbackLink - linkEP := loopback.New() + linkEP := ethernet.New(loopback.New()) if err := n.createNICWithAddrs(nicID, link.Name, linkEP, link.Addresses); err != nil { return nil, err } diff --git a/runsc/boot/network.go b/runsc/boot/network.go index 7e627e4c6..5c6879198 100644 --- a/runsc/boot/network.go +++ b/runsc/boot/network.go @@ -23,6 +23,7 @@ import ( "golang.org/x/sys/unix" "gvisor.dev/gvisor/pkg/log" "gvisor.dev/gvisor/pkg/tcpip" + "gvisor.dev/gvisor/pkg/tcpip/link/ethernet" "gvisor.dev/gvisor/pkg/tcpip/link/fdbased" "gvisor.dev/gvisor/pkg/tcpip/link/loopback" "gvisor.dev/gvisor/pkg/tcpip/link/packetsocket" @@ -169,7 +170,7 @@ func (n *Network) CreateLinksAndRoutes(args *CreateLinksAndRoutesArgs, _ *struct nicID++ nicids[link.Name] = nicID - linkEP := loopback.New() + linkEP := ethernet.New(loopback.New()) log.Infof("Enabling loopback interface %q with id %d on addresses %+v", link.Name, nicID, link.Addresses) if err := n.createNICWithAddrs(nicID, link.Name, linkEP, link.Addresses); err != nil { -- cgit v1.2.3