ipv6: Add hop-by-hop header to jumbograms in ip6_output

Instead of simply forcing a 0 payload_len in IPv6 header,
implement RFC 2675 and insert a custom extension header.

Note that only TCP stack is currently potentially generating
jumbograms, and that this extension header is purely local,
it wont be sent on a physical link.

This is needed so that packet capture (tcpdump and friends)
can properly dissect these large packets.

Signed-off-by: Coco Li <lixiaoyan@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index ec5ca392eaa31e83a022b1124fae6b607ba168cd..38c8203d52cbf39e523c43fe630a7b184b9991aa 100644 (file)
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -145,6 +145,7 @@ struct inet6_skb_parm {
 #define IP6SKB_L3SLAVE         64
 #define IP6SKB_JUMBOGRAM      128
 #define IP6SKB_SEG6          256
+#define IP6SKB_FAKEJUMBO      512
 };
 
 #if defined(CONFIG_NET_L3_MASTER_DEV)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index afa5bd4ad167c4a40878f33773d43be85e89c32f..4081b12a01ff22ecf94a6490aef0665808407a6e 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -182,7 +182,9 @@ static int __ip6_finish_output(struct net *net, struct sock *sk, struct sk_buff
 #endif
 
        mtu = ip6_skb_dst_mtu(skb);
-       if (skb_is_gso(skb) && !skb_gso_validate_network_len(skb, mtu))
+       if (skb_is_gso(skb) &&
+           !(IP6CB(skb)->flags & IP6SKB_FAKEJUMBO) &&
+           !skb_gso_validate_network_len(skb, mtu))
                return ip6_finish_output_gso_slowpath_drop(net, sk, skb, mtu);
 
        if ((skb->len > mtu && !skb_is_gso(skb)) ||
@@ -252,6 +254,8 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
        struct dst_entry *dst = skb_dst(skb);
        struct net_device *dev = dst->dev;
        struct inet6_dev *idev = ip6_dst_idev(dst);
+       struct hop_jumbo_hdr *hop_jumbo;
+       int hoplen = sizeof(*hop_jumbo);
        unsigned int head_room;
        struct ipv6hdr *hdr;
        u8  proto = fl6->flowi6_proto;
@@ -259,7 +263,7 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
        int hlimit = -1;
        u32 mtu;
 
-       head_room = sizeof(struct ipv6hdr) + LL_RESERVED_SPACE(dev);
+       head_room = sizeof(struct ipv6hdr) + hoplen + LL_RESERVED_SPACE(dev);
        if (opt)
                head_room += opt->opt_nflen + opt->opt_flen;
 
@@ -282,6 +286,20 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
                                             &fl6->saddr);
        }
 
+       if (unlikely(seg_len > IPV6_MAXPLEN)) {
+               hop_jumbo = skb_push(skb, hoplen);
+
+               hop_jumbo->nexthdr = proto;
+               hop_jumbo->hdrlen = 0;
+               hop_jumbo->tlv_type = IPV6_TLV_JUMBO;
+               hop_jumbo->tlv_len = 4;
+               hop_jumbo->jumbo_payload_len = htonl(seg_len + hoplen);
+
+               proto = IPPROTO_HOPOPTS;
+               seg_len = 0;
+               IP6CB(skb)->flags |= IP6SKB_FAKEJUMBO;
+       }
+
        skb_push(skb, sizeof(struct ipv6hdr));
        skb_reset_network_header(skb);
        hdr = ipv6_hdr(skb);