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/*-------------------------------------------------------------------------
*
* pqcomm.h
* Definitions common to frontends and backends.
*
* NOTE: for historical reasons, this does not correspond to pqcomm.c.
* pqcomm.c's routines are declared in libpq.h.
*
* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/libpq/pqcomm.h
*
*-------------------------------------------------------------------------
*/
#ifndef PQCOMM_H
#define PQCOMM_H
#include <sys/socket.h>
#include <sys/un.h>
#include <netdb.h>
#include <netinet/in.h>
/*
* The definitions for the request/response codes are kept in a separate file
* for ease of use in third party programs.
*/
#include "libpq/protocol.h"
typedef struct
{
struct sockaddr_storage addr;
socklen_t salen;
} SockAddr;
typedef struct
{
int family;
SockAddr addr;
} AddrInfo;
/* Configure the UNIX socket location for the well known port. */
#define UNIXSOCK_PATH(path, port, sockdir) \
(AssertMacro(sockdir), \
AssertMacro(*(sockdir) != '\0'), \
snprintf(path, sizeof(path), "%s/.s.PGSQL.%d", \
(sockdir), (port)))
/*
* The maximum workable length of a socket path is what will fit into
* struct sockaddr_un. This is usually only 100 or so bytes :-(.
*
* For consistency, always pass a MAXPGPATH-sized buffer to UNIXSOCK_PATH(),
* then complain if the resulting string is >= UNIXSOCK_PATH_BUFLEN bytes.
* (Because the standard API for getaddrinfo doesn't allow it to complain in
* a useful way when the socket pathname is too long, we have to test for
* this explicitly, instead of just letting the subroutine return an error.)
*/
#define UNIXSOCK_PATH_BUFLEN sizeof(((struct sockaddr_un *) NULL)->sun_path)
/*
* A host that looks either like an absolute path or starts with @ is
* interpreted as a Unix-domain socket address.
*/
static inline bool
is_unixsock_path(const char *path)
{
return is_absolute_path(path) || path[0] == '@';
}
/*
* These manipulate the frontend/backend protocol version number.
*
* The major number should be incremented for incompatible changes. The minor
* number should be incremented for compatible changes (eg. additional
* functionality).
*
* If a backend supports version m.n of the protocol it must actually support
* versions m.[0..n]. Backend support for version m-1 can be dropped after a
* `reasonable' length of time.
*
* A frontend isn't required to support anything other than the current
* version.
*/
#define PG_PROTOCOL_MAJOR(v) ((v) >> 16)
#define PG_PROTOCOL_MINOR(v) ((v) & 0x0000ffff)
#define PG_PROTOCOL_FULL(v) (PG_PROTOCOL_MAJOR(v) * 10000 + PG_PROTOCOL_MINOR(v))
#define PG_PROTOCOL(m,n) (((m) << 16) | (n))
/*
* The earliest and latest frontend/backend protocol version supported.
*/
#define PG_PROTOCOL_EARLIEST PG_PROTOCOL(3,0)
#define PG_PROTOCOL_LATEST PG_PROTOCOL(3,2)
typedef uint32 ProtocolVersion; /* FE/BE protocol version number */
typedef ProtocolVersion MsgType;
/*
* Packet lengths are 4 bytes in network byte order.
*
* The initial length is omitted from the packet layouts appearing below.
*/
typedef uint32 PacketLen;
/*
* In protocol 3.0 and later, the startup packet length is not fixed, but
* we set an arbitrary limit on it anyway. This is just to prevent simple
* denial-of-service attacks via sending enough data to run the server
* out of memory.
*/
#define MAX_STARTUP_PACKET_LENGTH 10000
typedef uint32 AuthRequest;
/*
* A client can also send a cancel-current-operation request to the postmaster.
* This is uglier than sending it directly to the client's backend, but it
* avoids depending on out-of-band communication facilities.
*
* The cancel request code must not match any protocol version number
* we're ever likely to use. This random choice should do.
*
* Before PostgreSQL v18 and the protocol version bump from 3.0 to 3.2, the
* cancel key was always 4 bytes. With protocol version 3.2, it's variable
* length.
*/
#define CANCEL_REQUEST_CODE PG_PROTOCOL(1234,5678)
typedef struct CancelRequestPacket
{
/* Note that each field is stored in network byte order! */
MsgType cancelRequestCode; /* code to identify a cancel request */
uint32 backendPID; /* PID of client's backend */
char cancelAuthCode[FLEXIBLE_ARRAY_MEMBER]; /* secret key to
* authorize cancel */
} CancelRequestPacket;
/* Application-Layer Protocol Negotiation is required for direct connections
* to avoid protocol confusion attacks (e.g https://alpaca-attack.com/).
*
* ALPN is specified in RFC 7301
*
* This string should be registered at:
* https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml#alpn-protocol-ids
*
* OpenSSL uses this wire-format for the list of alpn protocols even in the
* API. Both server and client take the same format parameter but the client
* actually sends it to the server as-is and the server it specifies the
* preference order to use to choose the one selected to send back.
*
* c.f. https://www.openssl.org/docs/manmaster/man3/SSL_CTX_set_alpn_select_cb.html
*
* The #define can be used to initialize a char[] vector to use directly in the API
*/
#define PG_ALPN_PROTOCOL "postgresql"
#define PG_ALPN_PROTOCOL_VECTOR { 10, 'p','o','s','t','g','r','e','s','q','l' }
/*
* A client can also start by sending a SSL or GSSAPI negotiation request to
* get a secure channel.
*/
#define NEGOTIATE_SSL_CODE PG_PROTOCOL(1234,5679)
#define NEGOTIATE_GSS_CODE PG_PROTOCOL(1234,5680)
#endif /* PQCOMM_H */
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