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authorPaolo Abeni <pabeni@redhat.com>2022-05-17 21:02:11 +0300
committerDavid S. Miller <davem@davemloft.net>2022-05-18 15:05:42 +0300
commitba2c89e0ea74a904d5231643245753d77422e7f5 (patch)
treecadd2fd0217592f637fa105a35e847eea3539989 /net/mptcp/options.c
parent680b892685ea7043addb5819ddec9147d4263195 (diff)
downloadlinux-ba2c89e0ea74a904d5231643245753d77422e7f5.tar.xz
mptcp: fix checksum byte order
The MPTCP code typecasts the checksum value to u16 and then converts it to big endian while storing the value into the MPTCP option. As a result, the wire encoding for little endian host is wrong, and that causes interoperabilty interoperability issues with other implementation or host with different endianness. Address the issue writing in the packet the unmodified __sum16 value. MPTCP checksum is disabled by default, interoperating with systems with bad mptcp-level csum encoding should cause fallback to TCP. Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/275 Fixes: c5b39e26d003 ("mptcp: send out checksum for DSS") Fixes: 390b95a5fb84 ("mptcp: receive checksum for DSS") Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/mptcp/options.c')
-rw-r--r--net/mptcp/options.c36
1 files changed, 24 insertions, 12 deletions
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 325383646f5c..b548cec86c9d 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -107,7 +107,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
ptr += 2;
}
if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
- mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
+ mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
ptr += 2;
}
@@ -221,7 +221,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
- mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
+ mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
ptr += 2;
}
@@ -1240,7 +1240,7 @@ static void mptcp_set_rwin(const struct tcp_sock *tp)
WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
}
-u16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
+__sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
{
struct csum_pseudo_header header;
__wsum csum;
@@ -1256,15 +1256,25 @@ u16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
header.csum = 0;
csum = csum_partial(&header, sizeof(header), sum);
- return (__force u16)csum_fold(csum);
+ return csum_fold(csum);
}
-static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
+static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext)
{
return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
~csum_unfold(mpext->csum));
}
+static void put_len_csum(u16 len, __sum16 csum, void *data)
+{
+ __sum16 *sumptr = data + 2;
+ __be16 *ptr = data;
+
+ put_unaligned_be16(len, ptr);
+
+ put_unaligned(csum, sumptr);
+}
+
void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
struct mptcp_out_options *opts)
{
@@ -1340,8 +1350,9 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
put_unaligned_be32(mpext->subflow_seq, ptr);
ptr += 1;
if (opts->csum_reqd) {
- put_unaligned_be32(mpext->data_len << 16 |
- mptcp_make_csum(mpext), ptr);
+ put_len_csum(mpext->data_len,
+ mptcp_make_csum(mpext),
+ ptr);
} else {
put_unaligned_be32(mpext->data_len << 16 |
TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
@@ -1392,11 +1403,12 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
goto mp_capable_done;
if (opts->csum_reqd) {
- put_unaligned_be32(opts->data_len << 16 |
- __mptcp_make_csum(opts->data_seq,
- opts->subflow_seq,
- opts->data_len,
- ~csum_unfold(opts->csum)), ptr);
+ put_len_csum(opts->data_len,
+ __mptcp_make_csum(opts->data_seq,
+ opts->subflow_seq,
+ opts->data_len,
+ ~csum_unfold(opts->csum)),
+ ptr);
} else {
put_unaligned_be32(opts->data_len << 16 |
TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);