On 12/14/2018 02:40 PM, Christoph Paasch wrote:
> Instead of having a single TFO-context, we now have a list of
> tcp_fastopen_context, bounded by TCP_FASTOPEN_CTXT_LEN (set to 2).
>
> This enables us to do a rolling TFO-key update that allows the server to
> accept old cookies and at the same time announce new ones to the client
> (see follow-up patch).
>
> Signed-off-by: Christoph Paasch <cpaa...@apple.com>
> ---
> include/net/tcp.h | 2 ++
> net/ipv4/tcp_fastopen.c | 52
> +++++++++++++++++++++++++++++++++++++++++++++----
> 2 files changed, 50 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index e0a65c067662..e629ea2e6c9d 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -1622,9 +1622,11 @@ bool tcp_fastopen_cookie_check(struct sock *sk, u16
> *mss,
> struct tcp_fastopen_cookie *cookie);
> bool tcp_fastopen_defer_connect(struct sock *sk, int *err);
> #define TCP_FASTOPEN_KEY_LENGTH 16
> +#define TCP_FASTOPEN_CTXT_LEN 2
>
> /* Fastopen key context */
> struct tcp_fastopen_context {
> + struct tcp_fastopen_context __rcu *next;
> struct crypto_cipher *tfm;
> __u8 key[TCP_FASTOPEN_KEY_LENGTH];
> struct rcu_head rcu;
> diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
> index 018a48477355..c52d5b8eabf0 100644
> --- a/net/ipv4/tcp_fastopen.c
> +++ b/net/ipv4/tcp_fastopen.c
> @@ -37,8 +37,14 @@ static void tcp_fastopen_ctx_free(struct rcu_head *head)
> {
> struct tcp_fastopen_context *ctx =
> container_of(head, struct tcp_fastopen_context, rcu);
> - crypto_free_cipher(ctx->tfm);
> - kfree(ctx);
> +
> + while (ctx) {
> + struct tcp_fastopen_context *prev = ctx;
> + /* We own ctx, thus no need to hold the Fastopen-lock */
> + ctx = rcu_dereference_protected(ctx->next, 1);
> + crypto_free_cipher(prev->tfm);
> + kfree(prev);
> + }
>
It seems this function does not need to be changed, since at most one context
should be freed per run ?
