IP_PKTINFO

[kazu-yamamoto]

On Unix:

data IPv4PktInfo = IPv4PktInfo Int HostAddress HostAddress deriving (Eq)

On Windows:

data IPv4PktInfo = IPv4PktInfo ULONG HostAddress deriving (Eq)

This difference makes cross-platform usage impossible.

On Unix, in_pktinfo is defined as follows:

struct in_pktinfo {
    unsigned int   ipi_ifindex;  /* Interface index */
    struct in_addr ipi_spec_dst; /* Local address */
    struct in_addr ipi_addr;     /* Header Destination address */
};

[kazu-yamamoto]

• Would you tell me the definition of struct in_pktinfo on Windows?
• Can we replace ULONG with Int?

[Mistuke]

• Would you tell me the definition of struct in_pktinfo on Windows?

Definition is

typedef struct in_pktinfo {
  IN_ADDR ipi_addr;
  ULONG   ipi_ifindex;
} IN_PKTINFO, *PIN_PKTINFO;

• Can we replace ULONG with Int?

Windows is IL32P64 so this ULONG is 32-bits. however you have the signed vs unsigned mismatch here. I guess it could be Int as you probably won't have more than 2^30 interfaces assuming they are numbered sequentially.