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tcp: Use a struct to represent a saved_syn
The TCP_SAVE_SYN has both the network header and tcp header. The total length of the saved syn packet is currently stored in the first 4 bytes (u32) of an array and the actual packet data is stored after that. A later patch will add a bpf helper that allows to get the tcp header alone from the saved syn without the network header. It will be more convenient to have a direct offset to a specific header instead of re-parsing it. This requires to separately store the network hdrlen. The total header length (i.e. network + tcp) is still needed for the current usage in getsockopt. Although this total length can be obtained by looking into the tcphdr and then get the (th->doff << 2), this patch chooses to directly store the tcp hdrlen in the second four bytes of this newly created "struct saved_syn". By using a new struct, it can give a readable name to each individual header length. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20200820190014.2883694-1-kafai@fb.com
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@ -406,7 +406,7 @@ struct tcp_sock {
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* socket. Used to retransmit SYNACKs etc.
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*/
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struct request_sock __rcu *fastopen_rsk;
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u32 *saved_syn;
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struct saved_syn *saved_syn;
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};
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enum tsq_enum {
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@ -484,6 +484,11 @@ static inline void tcp_saved_syn_free(struct tcp_sock *tp)
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tp->saved_syn = NULL;
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}
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static inline u32 tcp_saved_syn_len(const struct saved_syn *saved_syn)
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{
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return saved_syn->network_hdrlen + saved_syn->tcp_hdrlen;
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}
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struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
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const struct sk_buff *orig_skb);
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@ -41,6 +41,12 @@ struct request_sock_ops {
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int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
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struct saved_syn {
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u32 network_hdrlen;
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u32 tcp_hdrlen;
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u8 data[];
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};
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/* struct request_sock - mini sock to represent a connection request
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*/
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struct request_sock {
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@ -60,7 +66,7 @@ struct request_sock {
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struct timer_list rsk_timer;
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const struct request_sock_ops *rsk_ops;
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struct sock *sk;
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u32 *saved_syn;
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struct saved_syn *saved_syn;
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u32 secid;
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u32 peer_secid;
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};
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@ -4550,9 +4550,9 @@ static int _bpf_getsockopt(struct sock *sk, int level, int optname,
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tp = tcp_sk(sk);
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if (optlen <= 0 || !tp->saved_syn ||
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optlen > tp->saved_syn[0])
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optlen > tcp_saved_syn_len(tp->saved_syn))
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goto err_clear;
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memcpy(optval, tp->saved_syn + 1, optlen);
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memcpy(optval, tp->saved_syn->data, optlen);
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break;
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default:
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goto err_clear;
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@ -3788,20 +3788,21 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
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lock_sock(sk);
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if (tp->saved_syn) {
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if (len < tp->saved_syn[0]) {
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if (put_user(tp->saved_syn[0], optlen)) {
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if (len < tcp_saved_syn_len(tp->saved_syn)) {
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if (put_user(tcp_saved_syn_len(tp->saved_syn),
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optlen)) {
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release_sock(sk);
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return -EFAULT;
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}
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release_sock(sk);
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return -EINVAL;
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}
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len = tp->saved_syn[0];
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len = tcp_saved_syn_len(tp->saved_syn);
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if (put_user(len, optlen)) {
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release_sock(sk);
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return -EFAULT;
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}
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if (copy_to_user(optval, tp->saved_syn + 1, len)) {
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if (copy_to_user(optval, tp->saved_syn->data, len)) {
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release_sock(sk);
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return -EFAULT;
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}
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@ -6599,13 +6599,15 @@ static void tcp_reqsk_record_syn(const struct sock *sk,
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{
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if (tcp_sk(sk)->save_syn) {
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u32 len = skb_network_header_len(skb) + tcp_hdrlen(skb);
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u32 *copy;
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struct saved_syn *saved_syn;
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copy = kmalloc(len + sizeof(u32), GFP_ATOMIC);
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if (copy) {
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copy[0] = len;
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memcpy(©[1], skb_network_header(skb), len);
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req->saved_syn = copy;
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saved_syn = kmalloc(struct_size(saved_syn, data, len),
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GFP_ATOMIC);
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if (saved_syn) {
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saved_syn->network_hdrlen = skb_network_header_len(skb);
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saved_syn->tcp_hdrlen = tcp_hdrlen(skb);
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memcpy(saved_syn->data, skb_network_header(skb), len);
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req->saved_syn = saved_syn;
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}
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}
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}
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