diff --git a/drivers/net/bareudp.c b/drivers/net/bareudp.c
index 3b6664c7e73cbaa82c2def48a21fb924d2e88abb..841910f1db6559e2871fe225a0ed657e49dd6a61 100644
--- a/drivers/net/bareudp.c
+++ b/drivers/net/bareudp.c
@@ -308,7 +308,7 @@ static int bareudp_xmit_skb(struct sk_buff *skb, struct net_device *dev,
return PTR_ERR(rt);
skb_tunnel_check_pmtu(skb, &rt->dst,
- BAREUDP_IPV4_HLEN + info->options_len);
+ BAREUDP_IPV4_HLEN + info->options_len, false);
sport = udp_flow_src_port(bareudp->net, skb,
bareudp->sport_min, USHRT_MAX,
@@ -369,7 +369,8 @@ static int bareudp6_xmit_skb(struct sk_buff *skb, struct net_device *dev,
if (IS_ERR(dst))
return PTR_ERR(dst);
- skb_tunnel_check_pmtu(skb, dst, BAREUDP_IPV6_HLEN + info->options_len);
+ skb_tunnel_check_pmtu(skb, dst, BAREUDP_IPV6_HLEN + info->options_len,
+ false);
sport = udp_flow_src_port(bareudp->net, skb,
bareudp->sport_min, USHRT_MAX,
diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index 017c13acc9119651e6ae7e02a461e103e5ba5b1f..de86b6d8213252995eda23e1073c7bb739e6b307 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -894,7 +894,7 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
return PTR_ERR(rt);
skb_tunnel_check_pmtu(skb, &rt->dst,
- GENEVE_IPV4_HLEN + info->options_len);
+ GENEVE_IPV4_HLEN + info->options_len, false);
sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
if (geneve->cfg.collect_md) {
@@ -955,7 +955,8 @@ static int geneve6_xmit_skb(struct sk_buff *skb, struct net_device *dev,
if (IS_ERR(dst))
return PTR_ERR(dst);
- skb_tunnel_check_pmtu(skb, dst, GENEVE_IPV6_HLEN + info->options_len);
+ skb_tunnel_check_pmtu(skb, dst, GENEVE_IPV6_HLEN + info->options_len,
+ false);
sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
if (geneve->cfg.collect_md) {
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 77658425db8a5802e9c670419215d84117d54c79..1432544da50726e2bda7a36ddc5dafd283d8580c 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -2720,7 +2720,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
}
ndst = &rt->dst;
- skb_tunnel_check_pmtu(skb, ndst, VXLAN_HEADROOM);
+ skb_tunnel_check_pmtu(skb, ndst, VXLAN_HEADROOM, false);
tos = ip_tunnel_ecn_encap(RT_TOS(tos), old_iph, skb);
ttl = ttl ? : ip4_dst_hoplimit(&rt->dst);
@@ -2760,7 +2760,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
goto out_unlock;
}
- skb_tunnel_check_pmtu(skb, ndst, VXLAN6_HEADROOM);
+ skb_tunnel_check_pmtu(skb, ndst, VXLAN6_HEADROOM, false);
tos = ip_tunnel_ecn_encap(RT_TOS(tos), old_iph, skb);
ttl = ttl ? : ip6_dst_hoplimit(ndst);
diff --git a/include/net/dst.h b/include/net/dst.h
index 852d8fb36ab72390c5f417eaff9f9580eac69429..6ae2e625050dbd9da571f5f75f36986d9b56c94c 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -535,14 +535,4 @@ static inline void skb_dst_update_pmtu_no_confirm(struct sk_buff *skb, u32 mtu)
dst->ops->update_pmtu(dst, NULL, skb, mtu, false);
}
-static inline void skb_tunnel_check_pmtu(struct sk_buff *skb,
- struct dst_entry *encap_dst,
- int headroom)
-{
- u32 encap_mtu = dst_mtu(encap_dst);
-
- if (skb->len > encap_mtu - headroom)
- skb_dst_update_pmtu_no_confirm(skb, encap_mtu - headroom);
-}
-
#endif /* _NET_DST_H */
diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
index 36025dea7612ac462a2582883a6ea1024c141081..02ccd32542d0addb47578c419dd77447e462eb68 100644
--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -420,6 +420,8 @@ void iptunnel_xmit(struct sock *sk, struct rtable *rt, struct sk_buff *skb,
u8 tos, u8 ttl, __be16 df, bool xnet);
struct metadata_dst *iptunnel_metadata_reply(struct metadata_dst *md,
gfp_t flags);
+int skb_tunnel_check_pmtu(struct sk_buff *skb, struct dst_entry *encap_dst,
+ int headroom, bool reply);
int iptunnel_handle_offloads(struct sk_buff *skb, int gso_type_mask);
diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c
index f8b419e2475c9f7ec55a2fb0e4c0906c1f5f7102..9ddee2a0c66d8560f0ec8bb6300267c166f5e977 100644
--- a/net/ipv4/ip_tunnel_core.c
+++ b/net/ipv4/ip_tunnel_core.c
@@ -184,6 +184,250 @@ int iptunnel_handle_offloads(struct sk_buff *skb,
}
EXPORT_SYMBOL_GPL(iptunnel_handle_offloads);
+/**
+ * iptunnel_pmtud_build_icmp() - Build ICMP error message for PMTUD
+ * @skb: Original packet with L2 header
+ * @mtu: MTU value for ICMP error
+ *
+ * Return: length on success, negative error code if message couldn't be built.
+ */
+static int iptunnel_pmtud_build_icmp(struct sk_buff *skb, int mtu)
+{
+ const struct iphdr *iph = ip_hdr(skb);
+ struct icmphdr *icmph;
+ struct iphdr *niph;
+ struct ethhdr eh;
+ int len, err;
+
+ if (!pskb_may_pull(skb, ETH_HLEN + sizeof(struct iphdr)))
+ return -EINVAL;
+
+ skb_copy_bits(skb, skb_mac_offset(skb), &eh, ETH_HLEN);
+ pskb_pull(skb, ETH_HLEN);
+ skb_reset_network_header(skb);
+
+ err = pskb_trim(skb, 576 - sizeof(*niph) - sizeof(*icmph));
+ if (err)
+ return err;
+
+ len = skb->len + sizeof(*icmph);
+ err = skb_cow(skb, sizeof(*niph) + sizeof(*icmph) + ETH_HLEN);
+ if (err)
+ return err;
+
+ icmph = skb_push(skb, sizeof(*icmph));
+ *icmph = (struct icmphdr) {
+ .type = ICMP_DEST_UNREACH,
+ .code = ICMP_FRAG_NEEDED,
+ .checksum = 0,
+ .un.frag.__unused = 0,
+ .un.frag.mtu = ntohs(mtu),
+ };
+ icmph->checksum = ip_compute_csum(icmph, len);
+ skb_reset_transport_header(skb);
+
+ niph = skb_push(skb, sizeof(*niph));
+ *niph = (struct iphdr) {
+ .ihl = sizeof(*niph) / 4u,
+ .version = 4,
+ .tos = 0,
+ .tot_len = htons(len + sizeof(*niph)),
+ .id = 0,
+ .frag_off = htons(IP_DF),
+ .ttl = iph->ttl,
+ .protocol = IPPROTO_ICMP,
+ .saddr = iph->daddr,
+ .daddr = iph->saddr,
+ };
+ ip_send_check(niph);
+ skb_reset_network_header(skb);
+
+ skb->ip_summed = CHECKSUM_NONE;
+
+ eth_header(skb, skb->dev, htons(eh.h_proto), eh.h_source, eh.h_dest, 0);
+ skb_reset_mac_header(skb);
+
+ return skb->len;
+}
+
+/**
+ * iptunnel_pmtud_check_icmp() - Trigger ICMP reply if needed and allowed
+ * @skb: Buffer being sent by encapsulation, L2 headers expected
+ * @mtu: Network MTU for path
+ *
+ * Return: 0 for no ICMP reply, length if built, negative value on error.
+ */
+static int iptunnel_pmtud_check_icmp(struct sk_buff *skb, int mtu)
+{
+ const struct icmphdr *icmph = icmp_hdr(skb);
+ const struct iphdr *iph = ip_hdr(skb);
+
+ if (mtu <= 576 || iph->frag_off != htons(IP_DF))
+ return 0;
+
+ if (ipv4_is_lbcast(iph->daddr) || ipv4_is_multicast(iph->daddr) ||
+ ipv4_is_zeronet(iph->saddr) || ipv4_is_loopback(iph->saddr) ||
+ ipv4_is_lbcast(iph->saddr) || ipv4_is_multicast(iph->saddr))
+ return 0;
+
+ if (iph->protocol == IPPROTO_ICMP && icmp_is_err(icmph->type))
+ return 0;
+
+ return iptunnel_pmtud_build_icmp(skb, mtu);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+/**
+ * iptunnel_pmtud_build_icmpv6() - Build ICMPv6 error message for PMTUD
+ * @skb: Original packet with L2 header
+ * @mtu: MTU value for ICMPv6 error
+ *
+ * Return: length on success, negative error code if message couldn't be built.
+ */
+static int iptunnel_pmtud_build_icmpv6(struct sk_buff *skb, int mtu)
+{
+ const struct ipv6hdr *ip6h = ipv6_hdr(skb);
+ struct icmp6hdr *icmp6h;
+ struct ipv6hdr *nip6h;
+ struct ethhdr eh;
+ int len, err;
+ __wsum csum;
+
+ if (!pskb_may_pull(skb, ETH_HLEN + sizeof(struct ipv6hdr)))
+ return -EINVAL;
+
+ skb_copy_bits(skb, skb_mac_offset(skb), &eh, ETH_HLEN);
+ pskb_pull(skb, ETH_HLEN);
+ skb_reset_network_header(skb);
+
+ err = pskb_trim(skb, IPV6_MIN_MTU - sizeof(*nip6h) - sizeof(*icmp6h));
+ if (err)
+ return err;
+
+ len = skb->len + sizeof(*icmp6h);
+ err = skb_cow(skb, sizeof(*nip6h) + sizeof(*icmp6h) + ETH_HLEN);
+ if (err)
+ return err;
+
+ icmp6h = skb_push(skb, sizeof(*icmp6h));
+ *icmp6h = (struct icmp6hdr) {
+ .icmp6_type = ICMPV6_PKT_TOOBIG,
+ .icmp6_code = 0,
+ .icmp6_cksum = 0,
+ .icmp6_mtu = htonl(mtu),
+ };
+ skb_reset_transport_header(skb);
+
+ nip6h = skb_push(skb, sizeof(*nip6h));
+ *nip6h = (struct ipv6hdr) {
+ .priority = 0,
+ .version = 6,
+ .flow_lbl = { 0 },
+ .payload_len = htons(len),
+ .nexthdr = IPPROTO_ICMPV6,
+ .hop_limit = ip6h->hop_limit,
+ .saddr = ip6h->daddr,
+ .daddr = ip6h->saddr,
+ };
+ skb_reset_network_header(skb);
+
+ csum = csum_partial(icmp6h, len, 0);
+ icmp6h->icmp6_cksum = csum_ipv6_magic(&nip6h->saddr, &nip6h->daddr, len,
+ IPPROTO_ICMPV6, csum);
+
+ skb->ip_summed = CHECKSUM_NONE;
+
+ eth_header(skb, skb->dev, htons(eh.h_proto), eh.h_source, eh.h_dest, 0);
+ skb_reset_mac_header(skb);
+
+ return skb->len;
+}
+
+/**
+ * iptunnel_pmtud_check_icmpv6() - Trigger ICMPv6 reply if needed and allowed
+ * @skb: Buffer being sent by encapsulation, L2 headers expected
+ * @mtu: Network MTU for path
+ *
+ * Return: 0 for no ICMPv6 reply, length if built, negative value on error.
+ */
+static int iptunnel_pmtud_check_icmpv6(struct sk_buff *skb, int mtu)
+{
+ const struct ipv6hdr *ip6h = ipv6_hdr(skb);
+ int stype = ipv6_addr_type(&ip6h->saddr);
+ u8 proto = ip6h->nexthdr;
+ __be16 frag_off;
+ int offset;
+
+ if (mtu <= IPV6_MIN_MTU)
+ return 0;
+
+ if (stype == IPV6_ADDR_ANY || stype == IPV6_ADDR_MULTICAST ||
+ stype == IPV6_ADDR_LOOPBACK)
+ return 0;
+
+ offset = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &proto,
+ &frag_off);
+ if (offset < 0 || (frag_off & htons(~0x7)))
+ return 0;
+
+ if (proto == IPPROTO_ICMPV6) {
+ struct icmp6hdr *icmp6h;
+
+ if (!pskb_may_pull(skb, skb_network_header(skb) +
+ offset + 1 - skb->data))
+ return 0;
+
+ icmp6h = (struct icmp6hdr *)(skb_network_header(skb) + offset);
+ if (icmpv6_is_err(icmp6h->icmp6_type) ||
+ icmp6h->icmp6_type == NDISC_REDIRECT)
+ return 0;
+ }
+
+ return iptunnel_pmtud_build_icmpv6(skb, mtu);
+}
+#endif /* IS_ENABLED(CONFIG_IPV6) */
+
+/**
+ * skb_tunnel_check_pmtu() - Check, update PMTU and trigger ICMP reply as needed
+ * @skb: Buffer being sent by encapsulation, L2 headers expected
+ * @encap_dst: Destination for tunnel encapsulation (outer IP)
+ * @headroom: Encapsulation header size, bytes
+ * @reply: Build matching ICMP or ICMPv6 message as a result
+ *
+ * L2 tunnel implementations that can carry IP and can be directly bridged
+ * (currently UDP tunnels) can't always rely on IP forwarding paths to handle
+ * PMTU discovery. In the bridged case, ICMP or ICMPv6 messages need to be built
+ * based on payload and sent back by the encapsulation itself.
+ *
+ * For routable interfaces, we just need to update the PMTU for the destination.
+ *
+ * Return: 0 if ICMP error not needed, length if built, negative value on error
+ */
+int skb_tunnel_check_pmtu(struct sk_buff *skb, struct dst_entry *encap_dst,
+ int headroom, bool reply)
+{
+ u32 mtu = dst_mtu(encap_dst) - headroom;
+
+ if ((skb_is_gso(skb) && skb_gso_validate_network_len(skb, mtu)) ||
+ (!skb_is_gso(skb) && (skb->len - skb_mac_header_len(skb)) <= mtu))
+ return 0;
+
+ skb_dst_update_pmtu_no_confirm(skb, mtu);
+
+ if (!reply || skb->pkt_type == PACKET_HOST)
+ return 0;
+
+ if (skb->protocol == htons(ETH_P_IP))
+ return iptunnel_pmtud_check_icmp(skb, mtu);
+
+#if IS_ENABLED(CONFIG_IPV6)
+ if (skb->protocol == htons(ETH_P_IPV6))
+ return iptunnel_pmtud_check_icmpv6(skb, mtu);
+#endif
+ return 0;
+}
+EXPORT_SYMBOL(skb_tunnel_check_pmtu);
+
/* Often modified stats are per cpu, other are shared (netdev->stats) */
void ip_tunnel_get_stats64(struct net_device *dev,
struct rtnl_link_stats64 *tot)