net: Avoid access icmp_err_convert when icmp code is ICMP_FRAG_NEEDED

There is no need to fetch errno and fatal info from icmp_err_convert when
icmp code is ICMP_FRAG_NEEDED.
Signed-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/raw.c

@@ -260,11 +260,12 @@ static void raw_err(struct sock *sk, struct sk_buff *skb, u32 info)
 		err = EHOSTUNREACH;
 		if (code > NR_ICMP_UNREACH)
 			break;
-		err = icmp_err_convert[code].errno;
-		harderr = icmp_err_convert[code].fatal;
 		if (code == ICMP_FRAG_NEEDED) {
 			harderr = inet->pmtudisc != IP_PMTUDISC_DONT;
 			err = EMSGSIZE;
+		} else {
+			err = icmp_err_convert[code].errno;
+			harderr = icmp_err_convert[code].fatal;
 		}
 	}