Add RFC 8335 (Probe) Request and Response Functionality #328
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nmeyerhans
reviewed
Apr 30, 2021
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At first glance it looks OK.
One question: When I run this code and inspect the transmitted packets using wireshark, I see the expected interface identification object, but then another unknown object:
ICMP Multi-Part Extensions
Version: 2
.... 0000 0011 1000 = Reserved: 0x038
[Checksum: [missing]]
[Checksum Status: Not present]
Interface Identification Object
Length: 8
Class: Interface Identification Object (3)
C-Type: 2 (Identifies Interface By Index)
Interface Index: 2
Unknown object (139/96) (truncated)
Length: 50720
Class: Unknown (139)
C-Type: 96
Data: 0000000071d10200000000001c1d1e1f202122232425262728292a2b2c2d2e2f30313233…
What is the second object? Is it expected?
Comment on lines
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| // return; | ||
| // static int once; | ||
| // static struct sock_filter insns[] = { | ||
| // BPF_STMT(BPF_LDX | BPF_B | BPF_MSH, 0), /* Skip IP header due BSD, see ping6. */ | ||
| // BPF_STMT(BPF_LD | BPF_H | BPF_IND, 4), /* Load icmp echo ident */ | ||
| // BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0xAAAA, 0, 1), /* Ours? */ | ||
| // BPF_STMT(BPF_RET | BPF_K, ~0U), /* Yes, it passes. */ | ||
| // BPF_STMT(BPF_LD | BPF_B | BPF_IND, 0), /* Load icmp type */ | ||
| // BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ICMP_ECHOREPLY, 1, 0), /* Echo? */ | ||
| // BPF_STMT(BPF_RET | BPF_K, 0xFFFFFFF), /* No. It passes. */ | ||
| // BPF_STMT(BPF_RET | BPF_K, 0) /* Echo with wrong ident. Reject. */ | ||
| // }; | ||
| // static struct sock_fprog filter = { | ||
| // sizeof insns / sizeof(insns[0]), | ||
| // insns | ||
| // }; | ||
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| // if (once) | ||
| // return; | ||
| // once = 1; | ||
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| // /* Patch bpflet for current identifier. */ | ||
| // insns[2] = (struct sock_filter)BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(rts->ident), 0, 1); | ||
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| // if (setsockopt(sock->fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter))) | ||
| // error(0, errno, _("WARNING: failed to install socket filter")); |
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This doesn't seem necessary.
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RFC 8335 describes the use of extended echo requests to probe specific network interfaces. This PR adds the -e flag to the ping command to probe specific interfaces and receive responses from those interfaces. Functionality for RFC 8335 was recently included in Linux net-next.
Usage:
ping -4 -e [interface] [address]
Interface can be specified by name, index, or address.
Example:
ping -4 -e 1 192.168.1.201
PING 192.168.1.201 (192.168.1.201) 56(84) bytes of data.
64 bytes from 192.168.1.201: icmp_seq=263 ttl=64
64 bytes from 192.168.1.201: icmp_seq=519 ttl=64
64 bytes from 192.168.1.201: icmp_seq=775 ttl=64
--- 192.168.1.201 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss