net: ipv6: add skb drop reasons to TLV parse

Replace kfree_skb() used in TLV encoded option header parsing with
kfree_skb_reason(). Following functions are involved:

ip6_parse_tlv()
ipv6_hop_ra()
ipv6_hop_ioam()
ipv6_hop_jumbo()
ipv6_hop_calipso()
ipv6_dest_hao()

Most skb drops during this process are regarded as 'InHdrErrors',
as 'IPSTATS_MIB_INHDRERRORS' is used when ip6_parse_tlv() fails,
which make we use 'SKB_DROP_REASON_IP_INHDR' correspondingly.

However, 'IP_INHDR' is a relatively general reason. Therefore, we
can use other reasons with higher priority in some cases. For example,
'SKB_DROP_REASON_UNHANDLED_PROTO' is used for unknown TLV options.
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Reviewed-by: Jiang Biao <benbjiang@tencent.com>
Reviewed-by: Hao Peng <flyingpeng@tencent.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/exthdrs.c

@@ -90,12 +90,13 @@ static bool ip6_tlvopt_unknown(struct sk_buff *skb, int optoff,
 			break;
 		fallthrough;
 	case 2: /* send ICMP PARM PROB regardless and drop packet */
-		icmpv6_param_prob(skb, ICMPV6_UNK_OPTION, optoff);
+		icmpv6_param_prob_reason(skb, ICMPV6_UNK_OPTION, optoff,
+					 SKB_DROP_REASON_UNHANDLED_PROTO);
 		return false;
 	}
 
 drop:
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_UNHANDLED_PROTO);
 	return false;
 }
 
@@ -218,7 +219,7 @@ static bool ip6_parse_tlv(bool hopbyhop,
 	if (len == 0)
 		return true;
 bad:
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_IP_INHDR);
 	return false;
 }
 
@@ -232,6 +233,7 @@ static bool ipv6_dest_hao(struct sk_buff *skb, int optoff)
 	struct ipv6_destopt_hao *hao;
 	struct inet6_skb_parm *opt = IP6CB(skb);
 	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
+	SKB_DR(reason);
 	int ret;
 
 	if (opt->dsthao) {
@@ -246,19 +248,23 @@ static bool ipv6_dest_hao(struct sk_buff *skb, int optoff)
 	if (hao->length != 16) {
 		net_dbg_ratelimited("hao invalid option length = %d\n",
 				    hao->length);
+		SKB_DR_SET(reason, IP_INHDR);
 		goto discard;
 	}
 
 	if (!(ipv6_addr_type(&hao->addr) & IPV6_ADDR_UNICAST)) {
 		net_dbg_ratelimited("hao is not an unicast addr: %pI6\n",
 				    &hao->addr);
+		SKB_DR_SET(reason, INVALID_PROTO);
 		goto discard;
 	}
 
 	ret = xfrm6_input_addr(skb, (xfrm_address_t *)&ipv6h->daddr,
 			       (xfrm_address_t *)&hao->addr, IPPROTO_DSTOPTS);
-	if (unlikely(ret < 0))
+	if (unlikely(ret < 0)) {
+		SKB_DR_SET(reason, XFRM_POLICY);
 		goto discard;
+	}
 
 	if (skb_cloned(skb)) {
 		if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
@@ -281,7 +287,7 @@ static bool ipv6_dest_hao(struct sk_buff *skb, int optoff)
 	return true;
 
  discard:
-	kfree_skb(skb);
+	kfree_skb_reason(skb, reason);
 	return false;
 }
 #endif
@@ -931,7 +937,7 @@ static bool ipv6_hop_ra(struct sk_buff *skb, int optoff)
 	}
 	net_dbg_ratelimited("ipv6_hop_ra: wrong RA length %d\n",
 			    nh[optoff + 1]);
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_IP_INHDR);
 	return false;
 }
 
@@ -985,7 +991,7 @@ static bool ipv6_hop_ioam(struct sk_buff *skb, int optoff)
 	return true;
 
 drop:
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_IP_INHDR);
 	return false;
 }
 
@@ -994,26 +1000,32 @@ static bool ipv6_hop_ioam(struct sk_buff *skb, int optoff)
 static bool ipv6_hop_jumbo(struct sk_buff *skb, int optoff)
 {
 	const unsigned char *nh = skb_network_header(skb);
+	SKB_DR(reason);
 	u32 pkt_len;
 
 	if (nh[optoff + 1] != 4 || (optoff & 3) != 2) {
 		net_dbg_ratelimited("ipv6_hop_jumbo: wrong jumbo opt length/alignment %d\n",
 				    nh[optoff+1]);
+		SKB_DR_SET(reason, IP_INHDR);
 		goto drop;
 	}
 
 	pkt_len = ntohl(*(__be32 *)(nh + optoff + 2));
 	if (pkt_len <= IPV6_MAXPLEN) {
-		icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, optoff+2);
+		icmpv6_param_prob_reason(skb, ICMPV6_HDR_FIELD, optoff + 2,
+					 SKB_DROP_REASON_IP_INHDR);
 		return false;
 	}
 	if (ipv6_hdr(skb)->payload_len) {
-		icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, optoff);
+		icmpv6_param_prob_reason(skb, ICMPV6_HDR_FIELD, optoff,
+					 SKB_DROP_REASON_IP_INHDR);
 		return false;
 	}
 
-	if (pkt_len > skb->len - sizeof(struct ipv6hdr))
+	if (pkt_len > skb->len - sizeof(struct ipv6hdr)) {
+		SKB_DR_SET(reason, PKT_TOO_SMALL);
 		goto drop;
+	}
 
 	if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
 		goto drop;
@@ -1022,7 +1034,7 @@ static bool ipv6_hop_jumbo(struct sk_buff *skb, int optoff)
 	return true;
 
 drop:
-	kfree_skb(skb);
+	kfree_skb_reason(skb, reason);
 	return false;
 }
 
@@ -1044,7 +1056,7 @@ static bool ipv6_hop_calipso(struct sk_buff *skb, int optoff)
 	return true;
 
 drop:
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_IP_INHDR);
 	return false;
 }