Commit 355a901e6cf1b2b763ec85caa2a9f04fbcc4ab4a ("tcp: make connect()
mem charging friendly") was backported to various stable branches:
v3.10.73: e64a85197b3f tcp: make connect() mem charging friendly
v3.12.40: d06381e8aac5 tcp: make connect() mem charging friendly
v3.14.37: 5a8e8f482b4a tcp: make connect() mem charging friendly
v3.18.11: e8f117f002ca tcp: make connect() mem charging friendly
v3.13.11-ckt19: de023863df9d tcp: make connect() mem charging friendly
v3.16.7-ckt9: bea5f6ef9fcb tcp: make connect() mem charging friendly
On the 3.16 branch, this has resulted in a regression for TCP Fast Open:
<https://bugs.debian.org/782515>. The BUG() at the top of
tcp_transmit_skb() fires as tcp_skb_pcount(skb) == 0.
tcp_send_syn_data() does:
memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
Since commit cd7d8498c9a5 ("tcp: change tcp_skb_pcount() location") this
is sufficient to set the GSO segment count correctly. But in older
branches (< 3.18) the GSO segment count in skb_shared_info is used and
is no longer copied by tcp_send_syn_data().
All the versions listed above, except v3.18.11, appear to have suffered
this regression.
Ben.
--
Ben Hutchings
Editing code like this is akin to sticking plasters on the bleeding stump
of a severed limb. - me, 29 June 1999
Attachment:
signature.asc
Description: This is a digitally signed message part