On Mon, Aug 14, 2023 at 11:23:49PM -0700, Martin KaFai Lau wrote:
On 8/11/23 7:54 PM, Geliang Tang wrote:
+static int verify_mptcpify(int server_fd) +{
- socklen_t optlen;
- char cmd[256];
- int protocol;
- int err = 0;
- optlen = sizeof(protocol);
- if (!ASSERT_OK(getsockopt(server_fd, SOL_SOCKET, SO_PROTOCOL, &protocol, &optlen),
"getsockopt(SOL_PROTOCOL)"))return -1;- if (!ASSERT_EQ(protocol, IPPROTO_MPTCP, "protocol isn't MPTCP"))
err++;- /* Output of nstat:
** #kernel* MPTcpExtMPCapableSYNACKRX 1 0.0*/- snprintf(cmd, sizeof(cmd),
"ip netns exec %s nstat -asz %s | awk '%s' | grep -q '%s'",NS_TEST, "MPTcpExtMPCapableSYNACKRX","NR==1 {next} {print $2}", "1");Is the mp-capable something that the regular mptcp user want to learn from a fd also? Does it have a simpler way like to learn this, eg. getsockopt(fd, SOL_MPTCP, MPTCP_xxx), instead of parsing text output?
Thanks Martin. Yes, you're right. A better one is using getsockopt (MPTCP_INFO) to get the mptcpi_flags, then test the FALLBACK bit to make sure this MPTCP connection didn't fallback. This is, in other word, this MPTCP connection has been established correctly. Something like this:
+ optlen = sizeof(info); + if (!ASSERT_OK(getsockopt(fd, SOL_MPTCP, MPTCP_INFO, &info, &optlen), + "getsockopt(MPTCP_INFO)")) + return -1; + + if (!ASSERT_FALSE(info.mptcpi_flags & MPTCP_INFO_FLAG_FALLBACK, + "MPTCP fallback")) + err++;
It's necessary to add this further check after the MPTCP protocol check using getsockopt(SOL_PROTOCOL). Since in some cases, the MPTCP protocol check is not enough. Say, if we change TCP protocol into MPTCP using "cgroup/sock_create", the hook of BPF_CGROUP_RUN_PROG_INET_SOCK in inet_create(), this place is too late to change the protocol. Although sk->sk_protocol is set to MPTCP correctly, and the MPTCP protocol check using getsockopt(SOL_PROTOCOL) will pass. This MPTCP connection will fallback to TCP connection. So this further check is needed.
-Geliang
- if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))