Fix my IPv4 address's missing periods
C (gcc/linux), 125 121 bytes

i;f(char*a){do{char*y=a,s[99],*x=inet_ntop(2,&amp;i,s,99);for(;*x&amp;&amp;!(*x^*y&amp;&amp;*x^46);++x)y+=*x==*y;*x|*y||puts(s);}while(++i);}


Loops over all possible IPv4 addresses, and does a custom comparison that skips over extra dots in the generated ip address (but not in the main comparison address) to decide whether to print or not. Very slow, but should finish within 1 hour on a reasonable PC.