tcp: allow MPTCP to update the announced window

The MPTCP RFC requires that the MPTCP-level receive window's right edge never moves backward. Currently the MPTCP code enforces such constraint while tracking the right edge, but it does not reflects it on the wire, as MPTCP lacks a suitable hook to update accordingly the TCP header. This change modifies the existing mptcp_write_options() hook, providing the current packet's TCP header to the MPTCP protocol, so that the next patch could implement the above mentioned constraint. No functional changes intended.

Paolo Abeni committed 4 years ago

Commit ea667581 parent 92be2f53 files · +10 −8Browse files

Unified · Split

3 files

include/net/mptcp.h +1 −1
net/ipv4/tcp_output.c +8 −6
net/mptcp/options.c +1 −1

include/net/mptcp.h+1−1

@@ -125,7 +125,7 @@ bool mptcp_established_options(struct sock sk, struct sk_buff skb, · 124 unmodified lines
125	struct mptcp_out_options *opts);	125	struct mptcp_out_options *opts);
126	bool mptcp_incoming_options(struct sock sk, struct sk_buff skb);	126	bool mptcp_incoming_options(struct sock sk, struct sk_buff skb);
127		127
128	void mptcp_write_options(__be32 ptr, const struct tcp_sock tp,	128	void mptcp_write_options(struct tcphdr th, __be32 ptr, struct tcp_sock *tp,
129	struct mptcp_out_options *opts);	129	struct mptcp_out_options *opts);
130		130
131	void mptcp_diag_fill_info(struct mptcp_sock msk, struct mptcp_info info);	131	void mptcp_diag_fill_info(struct mptcp_sock msk, struct mptcp_info info);

net/ipv4/tcp_output.c+8−6

 	struct mptcp_out_options mptcp;
 };
-static void mptcp_options_write(__be32 *ptr, const struct tcp_sock *tp,
+static void mptcp_options_write(struct tcphdr *th, __be32 *ptr,
+				struct tcp_sock *tp,
 				struct tcp_out_options *opts)
 {
 #if IS_ENABLED(CONFIG_MPTCP)
 	if (unlikely(OPTION_MPTCP & opts->options))
-		mptcp_write_options(ptr, tp, &opts->mptcp);
+		mptcp_write_options(th, ptr, tp, &opts->mptcp);
 #endif
 }
  * At least SACK_PERM as the first option is known to lead to a disaster
  * (but it may well be that other scenarios fail similarly).
  */
-static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
+static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
 			      struct tcp_out_options *opts)
 {
+	__be32 *ptr = (__be32 *)(th + 1);
 	u16 options = opts->options;	/* mungable copy */
 	if (unlikely(OPTION_MD5 & options)) {
 	smc_options_write(ptr, &options);
-	mptcp_options_write(ptr, tp, opts);
+	mptcp_options_write(th, ptr, tp, opts);
 }
 static void smc_set_option(const struct tcp_sock *tp,
 		th->window	= htons(min(tp->rcv_wnd, 65535U));
 	}
-	tcp_options_write((__be32 *)(th + 1), tp, &opts);
+	tcp_options_write(th, tp, &opts);
 #ifdef CONFIG_TCP_MD5SIG
 	/* Calculate the MD5 hash, as we have all we need now */
 	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
 	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
-	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
+	tcp_options_write(th, NULL, &opts);
 	th->doff = (tcp_header_size >> 2);
 	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);

net/mptcp/options.c+1−1

@@ -1265,7 +1265,7 @@ static u16 mptcp_make_csum(const struct mptcp_ext *mpext) · 1264 unmodified lines
1265	~csum_unfold(mpext->csum));	1265	~csum_unfold(mpext->csum));
1266	}	1266	}
1267		1267
1268	void mptcp_write_options(__be32 ptr, const struct tcp_sock tp,	1268	void mptcp_write_options(struct tcphdr th, __be32 ptr, struct tcp_sock *tp,
1269	struct mptcp_out_options *opts)	1269	struct mptcp_out_options *opts)
1270	{	1270	{
1271	const struct sock ssk = (const struct sock )tp;	1271	const struct sock ssk = (const struct sock )tp;