Bugs in if_nametoindex/if_indextoname

[wkozaczuk]

The implementation of if_nametoindex()/if_indextoname() copied from musl under libc/network/if_nametoindex.c and libc/network/if_indextoname.c has number of problems:

1. Both use AF_UNIX domain which is unsupported on OSv (see fd = socket(AF_UNIX, SOCK_DGRAM, 0)); instead we neeed to use AF_INET like if_nameindex uses - see c4df104)
2. Even after fixing the above, if_nametoindex returns strangely high number like 1082589186 for eth0 and 1082589185 for lo0; most likely it is caused by not zero-ing the index field (for example zeroing ifr.ifr_ifindex in if_nametoindex.c before calling ioctl() makes the code return correct 2 and 1 index; the correct fix should be somewhere in bsd/linuz compatibility layer code (bsd/sys/compat/linux/linux_ioctl.cc or bsd/sys/kern/sys_socket.cc or bsd/sys/net/if.cc).
3. The if_indextoname needs support in ioctl layer (see missing handling of SIOCGIFNAME in bsd/sys/compat/linux/linux_ioctl.cc).

[wkozaczuk]

It looks like all these issues are fixed in the IPV6 branch (see https://github.com/cloudius-systems/osv/blob/ipv6/libc/network/if_nametoindex.c and https://github.com/cloudius-systems/osv/blob/ipv6/libc/network/if_indextoname.c). Also, partial netlink support has been added in IPV6 branch and it will be necessary for an upgrade to latest musl whose if_nameindex.c depends on. So it looks more so we will also need to merge IPV6 branch into master.

[wkozaczuk]

Instead of merging the entire ipv6 branch, we could partially merge some of commits or possibly only non-IPV6 part of it:

• f1cd48e - netlink
• d35c3dd - Fix if_indextoname(), if_nametoindex()
• b687b7c - libc: Add IPv6 support to getifaddrs(), if_nameindex() using NETLINK socket
• ea13cb1 - bsd: Fix SIOCSIFNAME when using linux compatiblity socket