in current Linux, MPTCP peers advertising endpoints with port numbers use a sub-option length that wrongly accounts for the trailing TCP NOP. Also, receivers will only process incoming ADD_ADDR with port having such wrong sub-option length. Fix this, making ADD_ADDR compliant to RFC8684 ยง3.4.1.
this can be verified running tcpdump on the kselftests artifacts:
unpatched kernel: [root@bottarga mptcp]# tcpdump -tnnr unpatched.pcap | grep add-addr reading from file unpatched.pcap, link-type LINUX_SLL (Linux cooked v1), snapshot length 65535 IP 10.0.1.1.10000 > 10.0.1.2.53078: Flags [.], ack 101, win 509, options [nop,nop,TS val 214459678 ecr 521312851,mptcp add-addr v1 id 1 a00:201:2774:2d88:7436:85c3:17fd:101], length 0 IP 10.0.1.2.53078 > 10.0.1.1.10000: Flags [.], ack 101, win 502, options [nop,nop,TS val 521312852 ecr 214459678,mptcp add-addr[bad opt]]
patched kernel: [root@bottarga mptcp]# tcpdump -tnnr patched.pcap | grep add-addr reading from file patched.pcap, link-type LINUX_SLL (Linux cooked v1), snapshot length 65535 IP 10.0.1.1.10000 > 10.0.1.2.38178: Flags [.], ack 101, win 509, options [nop,nop,TS val 3728873902 ecr 2732713192,mptcp add-addr v1 id 1 10.0.2.1:10100 hmac 0xbccdfcbe59292a1f,nop,nop], length 0 IP 10.0.1.2.38178 > 10.0.1.1.10000: Flags [.], ack 101, win 502, options [nop,nop,TS val 2732713195 ecr 3728873902,mptcp add-addr v1-echo id 1 10.0.2.1:10100,nop,nop], length 0
Fixes: 22fb85ffaefb ("mptcp: add port support for ADD_ADDR suboption writing") CC: stable@vger.kernel.org # 5.11+ Reviewed-by: Mat Martineau mathew.j.martineau@linux.intel.com Acked-and-tested-by: Geliang Tang geliangtang@gmail.com Signed-off-by: Davide Caratti dcaratti@redhat.com --- net/mptcp/protocol.h | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 91827d949766..e21a5bc36cf0 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -52,14 +52,15 @@ #define TCPOLEN_MPTCP_DSS_MAP64 14 #define TCPOLEN_MPTCP_DSS_CHECKSUM 2 #define TCPOLEN_MPTCP_ADD_ADDR 16 -#define TCPOLEN_MPTCP_ADD_ADDR_PORT 20 +#define TCPOLEN_MPTCP_ADD_ADDR_PORT 18 #define TCPOLEN_MPTCP_ADD_ADDR_BASE 8 -#define TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT 12 +#define TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT 10 #define TCPOLEN_MPTCP_ADD_ADDR6 28 -#define TCPOLEN_MPTCP_ADD_ADDR6_PORT 32 +#define TCPOLEN_MPTCP_ADD_ADDR6_PORT 30 #define TCPOLEN_MPTCP_ADD_ADDR6_BASE 20 -#define TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT 24 -#define TCPOLEN_MPTCP_PORT_LEN 4 +#define TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT 22 +#define TCPOLEN_MPTCP_PORT_LEN 2 +#define TCPOLEN_MPTCP_PORT_ALIGN 2 #define TCPOLEN_MPTCP_RM_ADDR_BASE 4 #define TCPOLEN_MPTCP_PRIO 3 #define TCPOLEN_MPTCP_PRIO_ALIGN 4 @@ -701,8 +702,9 @@ static inline unsigned int mptcp_add_addr_len(int family, bool echo, bool port) len = TCPOLEN_MPTCP_ADD_ADDR6_BASE; if (!echo) len += MPTCPOPT_THMAC_LEN; + /* account for 2 trailing 'nop' options */ if (port) - len += TCPOLEN_MPTCP_PORT_LEN; + len += TCPOLEN_MPTCP_PORT_LEN + TCPOLEN_MPTCP_PORT_ALIGN;
return len; }