Commit 82a01ab3 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

tcp: gso: really support BIG TCP 



We missed that tcp_gso_segment() was assuming skb->len was smaller than 65535 :

oldlen = (u16)~skb->len;

This part came with commit 0718bcc0 ("[NET]: Fix CHECKSUM_HW GSO problems.")

This leads to wrong TCP checksum.

Adapt the code to accept arbitrary packet length.

v2:
  - use two csum_add() instead of csum_fold() (Alexander Duyck)
  - Change delta type to __wsum to reduce casts (Alexander Duyck)

Fixes: 09f3d1a3 ("ipv6/gso: remove temporary HBH/jumbo header")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarAlexander Duyck <alexanderduyck@fb.com>
Reviewed-by: default avatarSimon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230605161647.3624428-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent a2f4c143

net/ipv4/tcp_offload.c

+9 −10
Original line number Diff line number Diff line
@@ -60,12 +60,12 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb, 
	struct tcphdr *th;

	unsigned int thlen;

	unsigned int seq;

	__be32 delta;

	unsigned int oldlen;

	unsigned int mss;

	struct sk_buff *gso_skb = skb;

	__sum16 newcheck;

	bool ooo_okay, copy_destructor;

	__wsum delta;



	th = tcp_hdr(skb);

	thlen = th->doff * 4;
@@ -75,7 +75,7 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb, 
	if (!pskb_may_pull(skb, thlen))

		goto out;



	oldlen = (u16)~skb->len;

	oldlen = ~skb->len;

	__skb_pull(skb, thlen);



	mss = skb_shinfo(skb)->gso_size;
@@ -110,7 +110,7 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb, 
	if (skb_is_gso(segs))

		mss *= skb_shinfo(segs)->gso_segs;



	delta = htonl(oldlen + (thlen + mss));

	delta = (__force __wsum)htonl(oldlen + thlen + mss);



	skb = segs;

	th = tcp_hdr(skb);
@@ -119,8 +119,7 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb, 
	if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))

		tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);



	newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +

					       (__force u32)delta));

	newcheck = ~csum_fold(csum_add(csum_unfold(th->check), delta));



	while (skb->next) {

		th->fin = th->psh = 0;
@@ -165,11 +164,11 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb, 
			WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));

	}



	delta = htonl(oldlen + (skb_tail_pointer(skb) -

	delta = (__force __wsum)htonl(oldlen +

				      (skb_tail_pointer(skb) -

				       skb_transport_header(skb)) +

				      skb->data_len);

	th->check = ~csum_fold((__force __wsum)((__force u32)th->check +

				(__force u32)delta));

	th->check = ~csum_fold(csum_add(csum_unfold(th->check), delta));

	if (skb->ip_summed == CHECKSUM_PARTIAL)

		gso_reset_checksum(skb, ~th->check);

	else