diff options
| author | Ghanan Gowripalan <ghanan@google.com> | 2021-08-19 13:51:40 -0700 |
|---|---|---|
| committer | gVisor bot <gvisor-bot@google.com> | 2021-08-19 13:54:53 -0700 |
| commit | 3b4bb947517d0d9010120aaa1c3989fd6abf278e (patch) | |
| tree | 73fd56f5f9ea152954f6e789231bcb76577e47de /pkg/tcpip/header | |
| parent | 50ed6b2e0994225b9bffa63b57a42da2d05e02b9 (diff) | |
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: <LOOPBACK,UP,LOWER_UP> 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
Diffstat (limited to 'pkg/tcpip/header')
| -rw-r--r-- | pkg/tcpip/header/eth.go | 6 | ||||
| -rw-r--r-- | pkg/tcpip/header/eth_test.go | 4 |
2 files changed, 5 insertions, 5 deletions
diff --git a/pkg/tcpip/header/eth.go b/pkg/tcpip/header/eth.go index 95ade0e5c..1f18213e5 100644 --- a/pkg/tcpip/header/eth.go +++ b/pkg/tcpip/header/eth.go @@ -49,9 +49,9 @@ const ( // EthernetAddressSize is the size, in bytes, of an ethernet address. EthernetAddressSize = 6 - // unspecifiedEthernetAddress is the unspecified ethernet address + // UnspecifiedEthernetAddress is the unspecified ethernet address // (all bits set to 0). - unspecifiedEthernetAddress = tcpip.LinkAddress("\x00\x00\x00\x00\x00\x00") + UnspecifiedEthernetAddress = tcpip.LinkAddress("\x00\x00\x00\x00\x00\x00") // EthernetBroadcastAddress is an ethernet address that addresses every node // on a local link. @@ -134,7 +134,7 @@ func IsValidUnicastEthernetAddress(addr tcpip.LinkAddress) bool { return false } - if addr == unspecifiedEthernetAddress { + if addr == UnspecifiedEthernetAddress { return false } diff --git a/pkg/tcpip/header/eth_test.go b/pkg/tcpip/header/eth_test.go index bf9ccbf1a..adc04e855 100644 --- a/pkg/tcpip/header/eth_test.go +++ b/pkg/tcpip/header/eth_test.go @@ -44,7 +44,7 @@ func TestIsValidUnicastEthernetAddress(t *testing.T) { }, { "Unspecified", - unspecifiedEthernetAddress, + UnspecifiedEthernetAddress, false, }, { @@ -91,7 +91,7 @@ func TestIsMulticastEthernetAddress(t *testing.T) { }, { "Unspecified", - unspecifiedEthernetAddress, + UnspecifiedEthernetAddress, false, }, { |