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pping: Various minor fixes

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Perform various fixes and tweaks:
- Rename several defines to make them more informative
- Remove unrolling of loop in BPF programs
- Reuse defines for program sections between userspace and kernel
  space programs
- Perform fork+exec to run bpf_egress_loader script instead of
  system()
- Add comment to copied scripts indicating I've modified them
- Add pping.h and pping_helpers.h as dependencies in Makefile

Also, add a brief description of what PPing is and how it works to
README

Signed-off-by: Simon Sundberg <simon.sundberg@kau.se>
This commit is contained in:
Simon Sundberg
2021-01-26 18:34:23 +01:00
parent 71c6458712
commit 7410d5cc2c
10 changed files with 184 additions and 107 deletions
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82
pping/pping_helpers.h
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@@ -3,6 +3,8 @@
#define PPING_HELPERS_H
#include "pping.h"
#include <linux/tcp.h>
#define MAX_TCP_OPTIONS 10
static __always_inline int fill_ipv4_flow(struct ipv4_flow *flow, __u32 saddr,
@@ -14,53 +16,57 @@ static __always_inline int fill_ipv4_flow(struct ipv4_flow *flow, __u32 saddr,
flow->dport = dport;
return 0;
}
/*
* Parses the TSval and TSecr values from the TCP options field. If sucessful
* the TSval and TSecr values will be stored at tsval and tsecr (in network
* Parses the TSval and TSecr values from the TCP options field. If sucessful
* the TSval and TSecr values will be stored at tsval and tsecr (in network
* byte order).
* Returns 0 if sucessful and -1 on failure
*/
static __always_inline int parse_tcp_ts(struct tcphdr *tcph, void *data_end,
__u32 *tsval, __u32 *tsecr)
__u32 *tsval, __u32 *tsecr)
{
if (tcph + 1 > data_end)
return -1;
int len = tcph->doff << 2;
if (len <= sizeof(struct tcphdr)) // No TCP options
return -1;
void *pos = (void *)(tcph + 1);
void *opt_end = ((void *)tcph + len);
int len = tcph->doff << 2;
void *opt_end = (void *)tcph + len;
__u8 *pos = (__u8 *)(tcph + 1); //Current pos in TCP options
__u8 i, opt, opt_size;
#pragma unroll
for (i = 0; i < MAX_TCP_OPTIONS; i++) {
if (pos + 1 > opt_end || pos + 1 > data_end)
return -1;
opt = *(__u8 *)pos; // Save value to avoid future data_end comparisons
if (opt == 0) // Reached end of TCP options
return -1;
if (opt == 1) { // TCP NOP option - advance one byte
pos++;
continue;
}
// Option > 1, should have option size
if (pos + 2 > opt_end || pos + 2 > data_end)
return -1;
opt_size = *(__u8 *)(pos + 1); // Save value to avoid future data_end comparisons
// Option-kind is TCP timestap (yey!)
if (opt == 8 && opt_size == 10) {
if (pos + opt_size > opt_end ||
pos + opt_size > data_end)
return -1;
*tsval = *(__u32 *)(pos + 2);
*tsecr = *(__u32 *)(pos + 6);
return 0;
}
if (tcph + 1 > data_end || len <= sizeof(struct tcphdr))
return -1;
// Some other TCP option - advance option-length bytes
pos += opt_size;
}
return -1;
for (i = 0; i < MAX_TCP_OPTIONS; i++) {
if (pos + 1 > opt_end || pos + 1 > data_end)
return -1;
opt = *pos;
if (opt == 0) // Reached end of TCP options
return -1;
if (opt == 1) { // TCP NOP option - advance one byte
pos++;
continue;
}
// Option > 1, should have option size
if (pos + 2 > opt_end || pos + 2 > data_end)
return -1;
opt_size = *(pos + 1);
// Option-kind is TCP timestap (yey!)
if (opt == 8 && opt_size == 10) {
if (pos + opt_size > opt_end ||
pos + opt_size > data_end)
return -1;
*tsval = *(__u32 *)(pos + 2);
*tsecr = *(__u32 *)(pos + 6);
return 0;
}
// Some other TCP option - advance option-length bytes
pos += opt_size;
}
return -1;
}
#endif