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mptcp: receive checksum for MP_CAPABLE with data 

This patch added a new member named csum in struct mptcp_options_received.

When parsing the MP_CAPABLE with data, if the checksum is enabled,
adjust the expected_opsize. If the receiving option length matches the
length with the data checksum, get the checksum value and save it in
mp_opt->csum. And in mptcp_incoming_options, pass it to mpext->csum.

We always parse any csum/nocsum combination and delay the presence check
to later code, to allow reset if missing.

Additionally, in the TX path, use the newly introduce ext field to avoid
MPTCP csum recomputation on TCP retransmission and unneeded csum update
on when setting the data fin_flag.

Co-developed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Geliang Tang 2021-06-17 16:46:14 -07:00 committed by David S. Miller
parent 0625118115
commit 208e8f6692
3 changed files with 31 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/net/mptcp.h
View File

@ -32,7 +32,8 @@ struct mptcp_ext {
mpc_map:1,
frozen:1,
reset_transient:1;
u8 reset_reason:4;
u8 reset_reason:4,
csum_reqd:1;
};
#define MPTCP_RM_IDS_MAX 8

35
net/mptcp/options.c
View File

@ -44,7 +44,20 @@ static void mptcp_parse_option(const struct sk_buff *skb,
else
expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
}
if (opsize != expected_opsize)
/* Cfr RFC 8684 Section 3.3.0:
* If a checksum is present but its use had
* not been negotiated in the MP_CAPABLE handshake, the receiver MUST
* close the subflow with a RST, as it is not behaving as negotiated.
* 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 parse even option with mismatching csum presence, so that
* later in subflow_data_ready we can trigger the reset.
*/
if (opsize != expected_opsize &&
(expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA ||
opsize != TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM))
break;
/* try to be gentle vs future versions on the initial syn */
@ -66,11 +79,6 @@ static void mptcp_parse_option(const struct sk_buff *skb,
* 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."
*/
if (flags & MPTCP_CAP_CHECKSUM_REQD)
mp_opt->csum_reqd = 1;
@ -84,7 +92,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
mp_opt->rcvr_key = get_unaligned_be64(ptr);
ptr += 8;
}
if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA) {
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
@ -96,9 +104,14 @@ static void mptcp_parse_option(const struct sk_buff *skb,
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",
if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
mp_opt->csum_reqd = 1;
ptr += 2;
}
pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u",
version, flags, opsize, mp_opt->sndr_key,
mp_opt->rcvr_key, mp_opt->data_len);
mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum);
break;
case MPTCPOPT_MP_JOIN:
@ -1118,6 +1131,10 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
}
mpext->data_len = mp_opt.data_len;
mpext->use_map = 1;
mpext->csum_reqd = mp_opt.csum_reqd;
if (mpext->csum_reqd)
mpext->csum = mp_opt.csum;
}
}

3
net/mptcp/protocol.h
View File

@ -68,6 +68,8 @@
#define TCPOLEN_MPTCP_FASTCLOSE 12
#define TCPOLEN_MPTCP_RST 4
#define TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM (TCPOLEN_MPTCP_DSS_CHECKSUM + TCPOLEN_MPTCP_MPC_ACK_DATA)
/* MPTCP MP_JOIN flags */
#define MPTCPOPT_BACKUP BIT(0)
#define MPTCPOPT_HMAC_LEN 20
@ -124,6 +126,7 @@ struct mptcp_options_received {
u64 data_seq;
u32 subflow_seq;
u16 data_len;
__sum16 csum;
u16 mp_capable : 1,
mp_join : 1,
fastclose : 1,