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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>
This commit is contained in:
Coco Li 2022-05-13 11:34:04 -07:00 committed by David S. Miller
parent 0fe79f28bf
commit 80e425b613
2 changed files with 21 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/ipv6.h
View File

@ -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)

22
net/ipv6/ip6_output.c
View File

@ -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);