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-rw-r--r--net/mptcp/options.c586
1 files changed, 586 insertions, 0 deletions
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
new file mode 100644
index 000000000000..45acd877bef3
--- /dev/null
+++ b/net/mptcp/options.c
@@ -0,0 +1,586 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2017 - 2019, Intel Corporation.
+ */
+
+#include <linux/kernel.h>
+#include <net/tcp.h>
+#include <net/mptcp.h>
+#include "protocol.h"
+
+static bool mptcp_cap_flag_sha256(u8 flags)
+{
+ return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
+}
+
+void mptcp_parse_option(const struct sk_buff *skb, const unsigned char *ptr,
+ int opsize, struct tcp_options_received *opt_rx)
+{
+ struct mptcp_options_received *mp_opt = &opt_rx->mptcp;
+ u8 subtype = *ptr >> 4;
+ int expected_opsize;
+ u8 version;
+ u8 flags;
+
+ switch (subtype) {
+ case MPTCPOPT_MP_CAPABLE:
+ /* strict size checking */
+ if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
+ if (skb->len > tcp_hdr(skb)->doff << 2)
+ expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
+ else
+ expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
+ } else {
+ if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)
+ expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
+ else
+ expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
+ }
+ if (opsize != expected_opsize)
+ break;
+
+ /* try to be gentle vs future versions on the initial syn */
+ version = *ptr++ & MPTCP_VERSION_MASK;
+ if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
+ if (version != MPTCP_SUPPORTED_VERSION)
+ break;
+ } else if (version < MPTCP_SUPPORTED_VERSION) {
+ break;
+ }
+
+ flags = *ptr++;
+ if (!mptcp_cap_flag_sha256(flags) ||
+ (flags & MPTCP_CAP_EXTENSIBILITY))
+ break;
+
+ /* RFC 6824, Section 3.1:
+ * "For the Checksum Required bit (labeled "A"), if either
+ * host requires the use of checksums, checksums MUST be used.
+ * In other words, the only way for checksums not to be used
+ * is if both hosts in their SYNs set A=0."
+ *
+ * Section 3.3.0:
+ * "If a checksum is not present when its use has been
+ * negotiated, the receiver MUST close the subflow with a RST as
+ * it is considered broken."
+ *
+ * We don't implement DSS checksum - fall back to TCP.
+ */
+ if (flags & MPTCP_CAP_CHECKSUM_REQD)
+ break;
+
+ mp_opt->mp_capable = 1;
+ if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
+ mp_opt->sndr_key = get_unaligned_be64(ptr);
+ ptr += 8;
+ }
+ if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
+ mp_opt->rcvr_key = get_unaligned_be64(ptr);
+ ptr += 8;
+ }
+ if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA) {
+ /* Section 3.1.:
+ * "the data parameters in a MP_CAPABLE are semantically
+ * equivalent to those in a DSS option and can be used
+ * interchangeably."
+ */
+ mp_opt->dss = 1;
+ mp_opt->use_map = 1;
+ mp_opt->mpc_map = 1;
+ mp_opt->data_len = get_unaligned_be16(ptr);
+ ptr += 2;
+ }
+ pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d",
+ version, flags, opsize, mp_opt->sndr_key,
+ mp_opt->rcvr_key, mp_opt->data_len);
+ break;
+
+ case MPTCPOPT_DSS:
+ pr_debug("DSS");
+ ptr++;
+
+ /* we must clear 'mpc_map' be able to detect MP_CAPABLE
+ * map vs DSS map in mptcp_incoming_options(), and reconstruct
+ * map info accordingly
+ */
+ mp_opt->mpc_map = 0;
+ flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
+ mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
+ mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
+ mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
+ mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
+ mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
+
+ pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
+ mp_opt->data_fin, mp_opt->dsn64,
+ mp_opt->use_map, mp_opt->ack64,
+ mp_opt->use_ack);
+
+ expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
+
+ if (mp_opt->use_ack) {
+ if (mp_opt->ack64)
+ expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
+ else
+ expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
+ }
+
+ if (mp_opt->use_map) {
+ if (mp_opt->dsn64)
+ expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
+ else
+ expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
+ }
+
+ /* RFC 6824, Section 3.3:
+ * If a checksum is present, but its use had
+ * not been negotiated in the MP_CAPABLE handshake,
+ * the checksum field MUST be ignored.
+ */
+ if (opsize != expected_opsize &&
+ opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
+ break;
+
+ mp_opt->dss = 1;
+
+ if (mp_opt->use_ack) {
+ if (mp_opt->ack64) {
+ mp_opt->data_ack = get_unaligned_be64(ptr);
+ ptr += 8;
+ } else {
+ mp_opt->data_ack = get_unaligned_be32(ptr);
+ ptr += 4;
+ }
+
+ pr_debug("data_ack=%llu", mp_opt->data_ack);
+ }
+
+ if (mp_opt->use_map) {
+ if (mp_opt->dsn64) {
+ mp_opt->data_seq = get_unaligned_be64(ptr);
+ ptr += 8;
+ } else {
+ mp_opt->data_seq = get_unaligned_be32(ptr);
+ ptr += 4;
+ }
+
+ mp_opt->subflow_seq = get_unaligned_be32(ptr);
+ ptr += 4;
+
+ mp_opt->data_len = get_unaligned_be16(ptr);
+ ptr += 2;
+
+ pr_debug("data_seq=%llu subflow_seq=%u data_len=%u",
+ mp_opt->data_seq, mp_opt->subflow_seq,
+ mp_opt->data_len);
+ }
+
+ break;
+
+ default:
+ break;
+ }
+}
+
+void mptcp_get_options(const struct sk_buff *skb,
+ struct tcp_options_received *opt_rx)
+{
+ const unsigned char *ptr;
+ const struct tcphdr *th = tcp_hdr(skb);
+ int length = (th->doff * 4) - sizeof(struct tcphdr);
+
+ ptr = (const unsigned char *)(th + 1);
+
+ while (length > 0) {
+ int opcode = *ptr++;
+ int opsize;
+
+ switch (opcode) {
+ case TCPOPT_EOL:
+ return;
+ case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
+ length--;
+ continue;
+ default:
+ opsize = *ptr++;
+ if (opsize < 2) /* "silly options" */
+ return;
+ if (opsize > length)
+ return; /* don't parse partial options */
+ if (opcode == TCPOPT_MPTCP)
+ mptcp_parse_option(skb, ptr, opsize, opt_rx);
+ ptr += opsize - 2;
+ length -= opsize;
+ }
+ }
+}
+
+bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
+ unsigned int *size, struct mptcp_out_options *opts)
+{
+ struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+ /* we will use snd_isn to detect first pkt [re]transmission
+ * in mptcp_established_options_mp()
+ */
+ subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
+ if (subflow->request_mptcp) {
+ pr_debug("local_key=%llu", subflow->local_key);
+ opts->suboptions = OPTION_MPTCP_MPC_SYN;
+ opts->sndr_key = subflow->local_key;
+ *size = TCPOLEN_MPTCP_MPC_SYN;
+ return true;
+ }
+ return false;
+}
+
+void mptcp_rcv_synsent(struct sock *sk)
+{
+ struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ pr_debug("subflow=%p", subflow);
+ if (subflow->request_mptcp && tp->rx_opt.mptcp.mp_capable) {
+ subflow->mp_capable = 1;
+ subflow->can_ack = 1;
+ subflow->remote_key = tp->rx_opt.mptcp.sndr_key;
+ } else {
+ tcp_sk(sk)->is_mptcp = 0;
+ }
+}
+
+static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
+ unsigned int *size,
+ unsigned int remaining,
+ struct mptcp_out_options *opts)
+{
+ struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+ struct mptcp_ext *mpext;
+ unsigned int data_len;
+
+ pr_debug("subflow=%p fourth_ack=%d seq=%x:%x remaining=%d", subflow,
+ subflow->fourth_ack, subflow->snd_isn,
+ skb ? TCP_SKB_CB(skb)->seq : 0, remaining);
+
+ if (subflow->mp_capable && !subflow->fourth_ack && skb &&
+ subflow->snd_isn == TCP_SKB_CB(skb)->seq) {
+ /* When skb is not available, we better over-estimate the
+ * emitted options len. A full DSS option is longer than
+ * TCPOLEN_MPTCP_MPC_ACK_DATA, so let's the caller try to fit
+ * that.
+ */
+ mpext = mptcp_get_ext(skb);
+ data_len = mpext ? mpext->data_len : 0;
+
+ /* we will check ext_copy.data_len in mptcp_write_options() to
+ * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
+ * TCPOLEN_MPTCP_MPC_ACK
+ */
+ opts->ext_copy.data_len = data_len;
+ opts->suboptions = OPTION_MPTCP_MPC_ACK;
+ opts->sndr_key = subflow->local_key;
+ opts->rcvr_key = subflow->remote_key;
+
+ /* Section 3.1.
+ * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
+ * packets that start the first subflow of an MPTCP connection,
+ * as well as the first packet that carries data
+ */
+ if (data_len > 0)
+ *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
+ else
+ *size = TCPOLEN_MPTCP_MPC_ACK;
+
+ pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
+ subflow, subflow->local_key, subflow->remote_key,
+ data_len);
+
+ return true;
+ }
+ return false;
+}
+
+static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
+ struct mptcp_ext *ext)
+{
+ ext->data_fin = 1;
+
+ if (!ext->use_map) {
+ /* RFC6824 requires a DSS mapping with specific values
+ * if DATA_FIN is set but no data payload is mapped
+ */
+ ext->use_map = 1;
+ ext->dsn64 = 1;
+ ext->data_seq = mptcp_sk(subflow->conn)->write_seq;
+ ext->subflow_seq = 0;
+ ext->data_len = 1;
+ } else {
+ /* If there's an existing DSS mapping, DATA_FIN consumes
+ * 1 additional byte of mapping space.
+ */
+ ext->data_len++;
+ }
+}
+
+static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
+ unsigned int *size,
+ unsigned int remaining,
+ struct mptcp_out_options *opts)
+{
+ struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+ unsigned int dss_size = 0;
+ struct mptcp_ext *mpext;
+ struct mptcp_sock *msk;
+ unsigned int ack_size;
+ bool ret = false;
+ u8 tcp_fin;
+
+ if (skb) {
+ mpext = mptcp_get_ext(skb);
+ tcp_fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
+ } else {
+ mpext = NULL;
+ tcp_fin = 0;
+ }
+
+ if (!skb || (mpext && mpext->use_map) || tcp_fin) {
+ unsigned int map_size;
+
+ map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
+
+ remaining -= map_size;
+ dss_size = map_size;
+ if (mpext)
+ opts->ext_copy = *mpext;
+
+ if (skb && tcp_fin &&
+ subflow->conn->sk_state != TCP_ESTABLISHED)
+ mptcp_write_data_fin(subflow, &opts->ext_copy);
+ ret = true;
+ }
+
+ opts->ext_copy.use_ack = 0;
+ msk = mptcp_sk(subflow->conn);
+ if (!msk || !READ_ONCE(msk->can_ack)) {
+ *size = ALIGN(dss_size, 4);
+ return ret;
+ }
+
+ ack_size = TCPOLEN_MPTCP_DSS_ACK64;
+
+ /* Add kind/length/subtype/flag overhead if mapping is not populated */
+ if (dss_size == 0)
+ ack_size += TCPOLEN_MPTCP_DSS_BASE;
+
+ dss_size += ack_size;
+
+ opts->ext_copy.data_ack = msk->ack_seq;
+ opts->ext_copy.ack64 = 1;
+ opts->ext_copy.use_ack = 1;
+
+ *size = ALIGN(dss_size, 4);
+ return true;
+}
+
+bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
+ unsigned int *size, unsigned int remaining,
+ struct mptcp_out_options *opts)
+{
+ unsigned int opt_size = 0;
+ bool ret = false;
+
+ if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts))
+ ret = true;
+ else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining,
+ opts))
+ ret = true;
+
+ /* we reserved enough space for the above options, and exceeding the
+ * TCP option space would be fatal
+ */
+ if (WARN_ON_ONCE(opt_size > remaining))
+ return false;
+
+ *size += opt_size;
+ remaining -= opt_size;
+
+ return ret;
+}
+
+bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
+ struct mptcp_out_options *opts)
+{
+ struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+
+ if (subflow_req->mp_capable) {
+ opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
+ opts->sndr_key = subflow_req->local_key;
+ *size = TCPOLEN_MPTCP_MPC_SYNACK;
+ pr_debug("subflow_req=%p, local_key=%llu",
+ subflow_req, subflow_req->local_key);
+ return true;
+ }
+ return false;
+}
+
+static bool check_fourth_ack(struct mptcp_subflow_context *subflow,
+ struct sk_buff *skb,
+ struct mptcp_options_received *mp_opt)
+{
+ /* here we can process OoO, in-window pkts, only in-sequence 4th ack
+ * are relevant
+ */
+ if (likely(subflow->fourth_ack ||
+ TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1))
+ return true;
+
+ if (mp_opt->use_ack)
+ subflow->fourth_ack = 1;
+
+ if (subflow->can_ack)
+ return true;
+
+ /* If the first established packet does not contain MP_CAPABLE + data
+ * then fallback to TCP
+ */
+ if (!mp_opt->mp_capable) {
+ subflow->mp_capable = 0;
+ tcp_sk(mptcp_subflow_tcp_sock(subflow))->is_mptcp = 0;
+ return false;
+ }
+ subflow->remote_key = mp_opt->sndr_key;
+ subflow->can_ack = 1;
+ return true;
+}
+
+void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb,
+ struct tcp_options_received *opt_rx)
+{
+ struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+ struct mptcp_options_received *mp_opt;
+ struct mptcp_ext *mpext;
+
+ mp_opt = &opt_rx->mptcp;
+ if (!check_fourth_ack(subflow, skb, mp_opt))
+ return;
+
+ if (!mp_opt->dss)
+ return;
+
+ mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
+ if (!mpext)
+ return;
+
+ memset(mpext, 0, sizeof(*mpext));
+
+ if (mp_opt->use_map) {
+ if (mp_opt->mpc_map) {
+ /* this is an MP_CAPABLE carrying MPTCP data
+ * we know this map the first chunk of data
+ */
+ mptcp_crypto_key_sha(subflow->remote_key, NULL,
+ &mpext->data_seq);
+ mpext->data_seq++;
+ mpext->subflow_seq = 1;
+ mpext->dsn64 = 1;
+ mpext->mpc_map = 1;
+ } else {
+ mpext->data_seq = mp_opt->data_seq;
+ mpext->subflow_seq = mp_opt->subflow_seq;
+ mpext->dsn64 = mp_opt->dsn64;
+ }
+ mpext->data_len = mp_opt->data_len;
+ mpext->use_map = 1;
+ }
+
+ if (mp_opt->use_ack) {
+ mpext->data_ack = mp_opt->data_ack;
+ mpext->use_ack = 1;
+ mpext->ack64 = mp_opt->ack64;
+ }
+
+ mpext->data_fin = mp_opt->data_fin;
+}
+
+void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts)
+{
+ if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
+ OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
+ u8 len;
+
+ if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
+ len = TCPOLEN_MPTCP_MPC_SYN;
+ else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
+ len = TCPOLEN_MPTCP_MPC_SYNACK;
+ else if (opts->ext_copy.data_len)
+ len = TCPOLEN_MPTCP_MPC_ACK_DATA;
+ else
+ len = TCPOLEN_MPTCP_MPC_ACK;
+
+ *ptr++ = htonl((TCPOPT_MPTCP << 24) | (len << 16) |
+ (MPTCPOPT_MP_CAPABLE << 12) |
+ (MPTCP_SUPPORTED_VERSION << 8) |
+ MPTCP_CAP_HMAC_SHA256);
+
+ if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
+ opts->suboptions))
+ goto mp_capable_done;
+
+ put_unaligned_be64(opts->sndr_key, ptr);
+ ptr += 2;
+ if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
+ goto mp_capable_done;
+
+ put_unaligned_be64(opts->rcvr_key, ptr);
+ ptr += 2;
+ if (!opts->ext_copy.data_len)
+ goto mp_capable_done;
+
+ put_unaligned_be32(opts->ext_copy.data_len << 16 |
+ TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
+ ptr += 1;
+ }
+
+mp_capable_done:
+ if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
+ struct mptcp_ext *mpext = &opts->ext_copy;
+ u8 len = TCPOLEN_MPTCP_DSS_BASE;
+ u8 flags = 0;
+
+ if (mpext->use_ack) {
+ len += TCPOLEN_MPTCP_DSS_ACK64;
+ flags = MPTCP_DSS_HAS_ACK | MPTCP_DSS_ACK64;
+ }
+
+ if (mpext->use_map) {
+ len += TCPOLEN_MPTCP_DSS_MAP64;
+
+ /* Use only 64-bit mapping flags for now, add
+ * support for optional 32-bit mappings later.
+ */
+ flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
+ if (mpext->data_fin)
+ flags |= MPTCP_DSS_DATA_FIN;
+ }
+
+ *ptr++ = htonl((TCPOPT_MPTCP << 24) |
+ (len << 16) |
+ (MPTCPOPT_DSS << 12) |
+ (flags));
+
+ if (mpext->use_ack) {
+ put_unaligned_be64(mpext->data_ack, ptr);
+ ptr += 2;
+ }
+
+ if (mpext->use_map) {
+ put_unaligned_be64(mpext->data_seq, ptr);
+ ptr += 2;
+ put_unaligned_be32(mpext->subflow_seq, ptr);
+ ptr += 1;
+ put_unaligned_be32(mpext->data_len << 16 |
+ TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
+ }
+ }
+}