Hello,
On Mon, 1 Apr 2019, Eric Dumazet wrote:
> It turns out that struct ipv6_pinfo is not located as we think.
>
> inet6_sk_generic() and tcp_inet6_sk() disagree on 32bit kernels by 4-bytes,
> because struct tcp_sock has 8-bytes alignment,
> but ipv6_pinfo size is not a multiple of 8.
>
> sizeof(struct ipv6_pinfo): 116 (not padded to 8)
>
> I actually first coded tcp_inet6_sk() as this patch does, but thought
> that "container_of(tcp_sk(sk), struct tcp6_sock, tcp)" was cleaner.
>
> As Julian told me : Nobody should use tcp6_sock.inet6
> directly, it should be accessed via tcp_inet6_sk() or inet6_sk().
>
> This happened when we added the first u64 field in struct tcp_sock.
>
> Fixes: 93a77c11ae79 ("tcp: add tcp_inet6_sk() helper")
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> Bisected-by: Julian Anastasov <j...@ssi.bg>
> ---
> net/ipv6/tcp_ipv6.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index
> eec814fe53b817106bc1d1eaa89dadcb96c974fa..82018bdce863165eba72e1ccf0c12ee558042ae8
> 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -93,12 +93,13 @@ static struct tcp_md5sig_key *tcp_v6_md5_do_lookup(const
> struct sock *sk,
> /* Helper returning the inet6 address from a given tcp socket.
> * It can be used in TCP stack instead of inet6_sk(sk).
> * This avoids a dereference and allow compiler optimizations.
> + * It is a specialized version of inet6_sk_generic().
> */
> static struct ipv6_pinfo *tcp_inet6_sk(const struct sock *sk)
> {
> - struct tcp6_sock *tcp6 = container_of(tcp_sk(sk), struct tcp6_sock,
> tcp);
> + unsigned int offset = sizeof(struct tcp6_sock) - sizeof(struct
> ipv6_pinfo);
>
> - return &tcp6->inet6;
> + return (struct ipv6_pinfo *)(((u8 *)sk) + offset);
> }
>
> static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
Thanks Eric! It is working here.
Regards
--
Julian Anastasov <j...@ssi.bg>
