diff options
Diffstat (limited to 'Documentation/networking/ip-sysctl.txt')
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 45 |
1 files changed, 23 insertions, 22 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 9ae929395b24..3db8c67d2c8d 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -575,32 +575,33 @@ tcp_syncookies - BOOLEAN unconditionally generation of syncookies. tcp_fastopen - INTEGER - Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data - in the opening SYN packet. To use this feature, the client application - must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than - connect() to perform a TCP handshake automatically. + Enable TCP Fast Open (RFC7413) to send and accept data in the opening + SYN packet. - The values (bitmap) are - 1: Enables sending data in the opening SYN on the client w/ MSG_FASTOPEN. - 2: Enables TCP Fast Open on the server side, i.e., allowing data in - a SYN packet to be accepted and passed to the application before - 3-way hand shake finishes. - 4: Send data in the opening SYN regardless of cookie availability and - without a cookie option. - 0x100: Accept SYN data w/o validating the cookie. - 0x200: Accept data-in-SYN w/o any cookie option present. - 0x400/0x800: Enable Fast Open on all listeners regardless of the - TCP_FASTOPEN socket option. The two different flags designate two - different ways of setting max_qlen without the TCP_FASTOPEN socket - option. + The client support is enabled by flag 0x1 (on by default). The client + then must use sendmsg() or sendto() with the MSG_FASTOPEN flag, + rather than connect() to send data in SYN. - Default: 1 + The server support is enabled by flag 0x2 (off by default). Then + either enable for all listeners with another flag (0x400) or + enable individual listeners via TCP_FASTOPEN socket option with + the option value being the length of the syn-data backlog. - Note that the client & server side Fast Open flags (1 and 2 - respectively) must be also enabled before the rest of flags can take - effect. + The values (bitmap) are + 0x1: (client) enables sending data in the opening SYN on the client. + 0x2: (server) enables the server support, i.e., allowing data in + a SYN packet to be accepted and passed to the + application before 3-way handshake finishes. + 0x4: (client) send data in the opening SYN regardless of cookie + availability and without a cookie option. + 0x200: (server) accept data-in-SYN w/o any cookie option present. + 0x400: (server) enable all listeners to support Fast Open by + default without explicit TCP_FASTOPEN socket option. + + Default: 0x1 - See include/net/tcp.h and the code for more details. + Note that that additional client or server features are only + effective if the basic support (0x1 and 0x2) are enabled respectively. tcp_syn_retries - INTEGER Number of times initial SYNs for an active TCP connection attempt |