net/ipv4: Ensure that location of timestamp option is stored

This is needed in order to detect if the timestamp option appears
more than once in a packet, to remove the option if the packet is
fragmented, etc. My previous change neglected to store the option
location when the router addresses were prespecified and Pointer >
Length. But now the option location is also stored when Flag is an
unrecognized value, to ensure these option handling behaviors are
still performed.
Signed-off-by: NDavid Ward <david.ward@ll.mit.edu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ip_options.c

@@ -370,7 +370,6 @@ int ip_options_compile(struct net *net,
 				}
 				switch (optptr[3]&0xF) {
 				      case IPOPT_TS_TSONLY:
-					opt->ts = optptr - iph;
 					if (skb)
 						timeptr = &optptr[optptr[2]-1];
 					opt->ts_needtime = 1;
@@ -381,7 +380,6 @@ int ip_options_compile(struct net *net,
 						pp_ptr = optptr + 2;
 						goto error;
 					}
-					opt->ts = optptr - iph;
 					if (rt)  {
 						spec_dst_fill(&spec_dst, skb);
 						memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
@@ -396,7 +394,6 @@ int ip_options_compile(struct net *net,
 						pp_ptr = optptr + 2;
 						goto error;
 					}
-					opt->ts = optptr - iph;
 					{
 						__be32 addr;
 						memcpy(&addr, &optptr[optptr[2]-1], 4);
@@ -429,12 +426,12 @@ int ip_options_compile(struct net *net,
 					pp_ptr = optptr + 3;
 					goto error;
 				}
-				opt->ts = optptr - iph;
 				if (skb) {
 					optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 					opt->is_changed = 1;
 				}
 			}
+			opt->ts = optptr - iph;
 			break;
 		      case IPOPT_RA:
 			if (optlen < 4) {