Helper function bpf_tcp_gen_syncookie
Definition
Copyright (c) 2015 The Libbpf Authors. All rights reserved.
Try to issue a SYN cookie for the packet with corresponding IP/TCP headers, iph and th, on the listening socket in sk.
iph points to the start of the IPv4 or IPv6 header, while iph_len contains sizeof(struct iphdr) or sizeof(struct ipv6hdr).
th points to the start of the TCP header, while th_len contains the length of the TCP header with options (at least sizeof(struct tcphdr)).
Returns
On success, lower 32 bits hold the generated SYN cookie in followed by 16 bits which hold the MSS value for that cookie, and the top 16 bits are unused.
On failure, the returned value is one of the following:
-EINVAL SYN cookie cannot be issued due to error
-ENOENT SYN cookie should not be issued (no SYN flood)
-EOPNOTSUPP kernel configuration does not enable SYN cookies
-EPROTONOSUPPORT IP packet version is not 4 or 6
static __s64 (* const bpf_tcp_gen_syncookie)(void *sk, void *iph, __u32 iph_len, struct tcphdr *th, __u32 th_len) = (void *) 110;
Usage
Docs could be improved
This part of the docs is incomplete, contributions are very welcome
Program types
This helper call can be used in the following program types:
Example
Docs could be improved
This part of the docs is incomplete, contributions are very welcome