I tested the above kernel on a ThinkPad X1 Carbon 7th with a Thunderbolt Dock 2nd Gen.
Below it the result when inserting cable into local Ethernet:
u@u-ThinkPad-X1-Carbon-7th:~$ ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: enp0s31f6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 98:fa:9b:1d:f8:01 brd ff:ff:ff:ff:ff:ff inet 10.8.8.38/24 brd 10.8.8.255 scope global dynamic noprefixroute enp0s31f6 valid_lft 375sec preferred_lft 375sec inet6 fe80::5af7:b91b:8317:9006/64 scope link noprefixroute valid_lft forever preferred_lft forever 3: wlp0s20f3: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000 link/ether 38:00:25:62:c5:1e brd ff:ff:ff:ff:ff:ff
Below it the result when inserting cable into Dock Ethernet:
u@u-ThinkPad-X1-Carbon-7th:~$ ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: enp0s31f6: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000 link/ether 98:fa:9b:1d:f8:01 brd ff:ff:ff:ff:ff:ff 3: wlp0s20f3: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000 link/ether 38:00:25:62:c5:1e brd ff:ff:ff:ff:ff:ff 4: enxe04f439597fa: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether e0:4f:43:95:97:fa brd ff:ff:ff:ff:ff:ff inet 10.8.8.25/24 brd 10.8.8.255 scope global dynamic noprefixroute enxe04f439597fa valid_lft 582sec preferred_lft 582sec inet6 fe80::26ef:5ee3:a28b:3622/64 scope link noprefixroute valid_lft forever preferred_lft forever
Below it the result when inserting cable into Dock Ethernet and enabled Mac Pass Through in BIOS:
u@u-ThinkPad-X1-Carbon-7th:~$ ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: enp0s31f6: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000 link/ether 98:fa:9b:1d:f8:01 brd ff:ff:ff:ff:ff:ff 3: wlp0s20f3: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000 link/ether 38:00:25:62:c5:1e brd ff:ff:ff:ff:ff:ff 4: enxe04f439597fa: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether e0:4f:43:95:97:fa brd ff:ff:ff:ff:ff:ff inet 10.8.8.25/24 brd 10.8.8.255 scope global dynamic noprefixroute enxe04f439597fa valid_lft 184sec preferred_lft 184sec inet6 fe80::26ef:5ee3:a28b:3622/64 scope link noprefixroute valid_lft forever preferred_lft forever
so, in the 3rd testing, the IP still get from Dock's address e0:4f:43:95:97:fa, it seems the Mac Pass through did not work.
I tested the above kernel on a ThinkPad X1 Carbon 7th with a Thunderbolt Dock 2nd Gen.
Below it the result when inserting cable into local Ethernet:
u@u-ThinkPad- X1-Carbon- 7th:~$ ip a UP,LOWER_ UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 MULTICAST, UP,LOWER_ UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 b91b:8317: 9006/64 scope link noprefixroute BROADCAST, MULTICAST, UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
1: lo: <LOOPBACK,
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s31f6: <BROADCAST,
link/ether 98:fa:9b:1d:f8:01 brd ff:ff:ff:ff:ff:ff
inet 10.8.8.38/24 brd 10.8.8.255 scope global dynamic noprefixroute enp0s31f6
valid_lft 375sec preferred_lft 375sec
inet6 fe80::5af7:
valid_lft forever preferred_lft forever
3: wlp0s20f3: <NO-CARRIER,
link/ether 38:00:25:62:c5:1e brd ff:ff:ff:ff:ff:ff
Below it the result when inserting cable into Dock Ethernet:
u@u-ThinkPad- X1-Carbon- 7th:~$ ip a UP,LOWER_ UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 BROADCAST, MULTICAST, UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000 BROADCAST, MULTICAST, UP> mtu 1500 qdisc mq state DOWN group default qlen 1000 MULTICAST, UP,LOWER_ UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 5ee3:a28b: 3622/64 scope link noprefixroute
1: lo: <LOOPBACK,
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s31f6: <NO-CARRIER,
link/ether 98:fa:9b:1d:f8:01 brd ff:ff:ff:ff:ff:ff
3: wlp0s20f3: <NO-CARRIER,
link/ether 38:00:25:62:c5:1e brd ff:ff:ff:ff:ff:ff
4: enxe04f439597fa: <BROADCAST,
link/ether e0:4f:43:95:97:fa brd ff:ff:ff:ff:ff:ff
inet 10.8.8.25/24 brd 10.8.8.255 scope global dynamic noprefixroute enxe04f439597fa
valid_lft 582sec preferred_lft 582sec
inet6 fe80::26ef:
valid_lft forever preferred_lft forever
Below it the result when inserting cable into Dock Ethernet and enabled Mac Pass Through in BIOS:
u@u-ThinkPad- X1-Carbon- 7th:~$ ip a UP,LOWER_ UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 BROADCAST, MULTICAST, UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000 BROADCAST, MULTICAST, UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000 MULTICAST, UP,LOWER_ UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 5ee3:a28b: 3622/64 scope link noprefixroute
1: lo: <LOOPBACK,
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s31f6: <NO-CARRIER,
link/ether 98:fa:9b:1d:f8:01 brd ff:ff:ff:ff:ff:ff
3: wlp0s20f3: <NO-CARRIER,
link/ether 38:00:25:62:c5:1e brd ff:ff:ff:ff:ff:ff
4: enxe04f439597fa: <BROADCAST,
link/ether e0:4f:43:95:97:fa brd ff:ff:ff:ff:ff:ff
inet 10.8.8.25/24 brd 10.8.8.255 scope global dynamic noprefixroute enxe04f439597fa
valid_lft 184sec preferred_lft 184sec
inet6 fe80::26ef:
valid_lft forever preferred_lft forever
so, in the 3rd testing, the IP still get from Dock's address e0:4f:43:95:97:fa, it seems the Mac Pass through did not work.