It's a common pattern in test code to reinterpret_cast<sockaddr*> from
sockaddr_* structs. Make AsSockAddr() for them so code looks better.
Note: Why not a wrapper type for `sockaddr_storage` and etc?
It's also a common need to have a local in-out variable of socklen_t.
Creating a wrapper type may however lead to this wrong code:
Wrapper addr;
socklen_t addrlen = sizeof(addr);
where sizeof(Wrapper) may not equal to sizeof(sockaddr_storage).
PiperOrigin-RevId: 368126229
An earlier change considered the loopback bound to all addresses in an
assigned subnet. This should have only be done for IPv4 to maintain
compatability with Linux:
```
$ ip addr show dev lo
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group ...
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
$ ping 2001:db8::1
PING 2001:db8::1(2001:db8::1) 56 data bytes
^C
--- 2001:db8::1 ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 3062ms
$ ping 2001:db8::2
PING 2001:db8::2(2001:db8::2) 56 data bytes
^C
--- 2001:db8::2 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2030ms
$ sudo ip addr add 2001:db8::1/64 dev lo
$ ping 2001:db8::1
PING 2001:db8::1(2001:db8::1) 56 data bytes
64 bytes from 2001:db8::1: icmp_seq=1 ttl=64 time=0.055 ms
64 bytes from 2001:db8::1: icmp_seq=2 ttl=64 time=0.074 ms
64 bytes from 2001:db8::1: icmp_seq=3 ttl=64 time=0.073 ms
64 bytes from 2001:db8::1: icmp_seq=4 ttl=64 time=0.071 ms
^C
--- 2001:db8::1 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3075ms
rtt min/avg/max/mdev = 0.055/0.068/0.074/0.007 ms
$ ping 2001:db8::2
PING 2001:db8::2(2001:db8::2) 56 data bytes
From 2001:db8::1 icmp_seq=1 Destination unreachable: No route
From 2001:db8::1 icmp_seq=2 Destination unreachable: No route
From 2001:db8::1 icmp_seq=3 Destination unreachable: No route
From 2001:db8::1 icmp_seq=4 Destination unreachable: No route
^C
--- 2001:db8::2 ping statistics ---
4 packets transmitted, 0 received, +4 errors, 100% packet loss, time 3070ms
```
Test: integration_test.TestLoopbackAcceptAllInSubnet
PiperOrigin-RevId: 329011566
...while we figure out of we want to consider the loopback interface
bound to all IPs in an assigned IPv6 subnet, or not (to maintain
compatibility with Linux).
PiperOrigin-RevId: 328807974
When a loopback interface is configurd with an address and associated
subnet, the loopback should treat all addresses in that subnet as an
address it owns.
This is mimicking linux behaviour as seen below:
```
$ ip addr show dev lo
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group ...
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
$ ping 192.0.2.1
PING 192.0.2.1 (192.0.2.1) 56(84) bytes of data.
^C
--- 192.0.2.1 ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 1018ms
$ ping 192.0.2.2
PING 192.0.2.2 (192.0.2.2) 56(84) bytes of data.
^C
--- 192.0.2.2 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2039ms
$ sudo ip addr add 192.0.2.1/24 dev lo
$ ip addr show dev lo
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group ...
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
inet 192.0.2.1/24 scope global lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
$ ping 192.0.2.1
PING 192.0.2.1 (192.0.2.1) 56(84) bytes of data.
64 bytes from 192.0.2.1: icmp_seq=1 ttl=64 time=0.131 ms
64 bytes from 192.0.2.1: icmp_seq=2 ttl=64 time=0.046 ms
64 bytes from 192.0.2.1: icmp_seq=3 ttl=64 time=0.048 ms
^C
--- 192.0.2.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2042ms
rtt min/avg/max/mdev = 0.046/0.075/0.131/0.039 ms
$ ping 192.0.2.2
PING 192.0.2.2 (192.0.2.2) 56(84) bytes of data.
64 bytes from 192.0.2.2: icmp_seq=1 ttl=64 time=0.131 ms
64 bytes from 192.0.2.2: icmp_seq=2 ttl=64 time=0.069 ms
64 bytes from 192.0.2.2: icmp_seq=3 ttl=64 time=0.049 ms
64 bytes from 192.0.2.2: icmp_seq=4 ttl=64 time=0.035 ms
^C
--- 192.0.2.2 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3049ms
rtt min/avg/max/mdev = 0.035/0.071/0.131/0.036 ms
```
Test: integration_test.TestLoopbackAcceptAllInSubnet
PiperOrigin-RevId: 328188546
Ting-Yu Wang
Ghanan Gowripalan