--- name: "pipex" section: "4" platform: "openbsd" package: "man" version: "8.0-current-20261101" release: "OpenBSD 8.0-current (2026-11-01)" platforms: ["openbsd"] url: "https://new.carta.tech/pipex" --- # pipex(4) PPP IP EXtension to handle IP/PPP frames in-kernel ## NAME **pipex** – PPP IP EXtension to handle IP/PPP frames in-kernel ## SYNOPSIS **option PIPEX** **#include \** **#include \** **#include \** **#include \** **#include \** ## DESCRIPTION **pipex** is used with pppac(4) and [pppx(4)](/pppx/4.md), and handles PPP frames and forwards IP packets in-kernel. It accelerates the performance of packet forwarding, because it reduces copying of packets between kernel and userland. **pipex** is disabled by default. To enable it, set *net.pipex.enable* to ‘1’ using [sysctl(8)](/sysctl/8.md). **pipex** adds some extensions to the [ioctl(2)](/ioctl/2.md) requests to pppac(4) or [pppx(4)](/pppx/4.md) devices. The added requests are as follows: - PIPEXASESSION *struct pipex\_session\_req \** Add a new PPP session to be handled by **pipex**. The status of the session is passed as a *pipex\_session\_req* structure. The *pipex\_session\_req* structure has the following definition: ``` struct pipex_session_req { int pr_protocol; /* tunnel protocol */ #define PIPEX_PROTO_L2TP 1 /* protocol L2TP */ #define PIPEX_PROTO_PPTP 2 /* protocol PPTP */ #define PIPEX_PROTO_PPPOE 3 /* protocol PPPoE */ uint16_t pr_session_id; /* session-id */ uint16_t pr_peer_session_id; /* peer's session-id */ uint32_t pr_ppp_flags; /* ppp configuration flags */ #define PIPEX_PPP_ACFC_ACCEPTED 0x0001 /* ACFC accepted */ #define PIPEX_PPP_PFC_ACCEPTED 0x0002 /* PFC accepted */ #define PIPEX_PPP_ACFC_ENABLED 0x0004 /* ACFC enabled */ #define PIPEX_PPP_PFC_ENABLED 0x0008 /* PFC enabled */ #define PIPEX_PPP_MPPE_ACCEPTED 0x0010 /* MPPE accepted */ #define PIPEX_PPP_MPPE_ENABLED 0x0020 /* MPPE enabled */ #define PIPEX_PPP_MPPE_REQUIRED 0x0040 /* MPPE is required */ #define PIPEX_PPP_HAS_ACF 0x0080 /* has ACF */ #define PIPEX_PPP_ADJUST_TCPMSS 0x0100 /* do tcpmss adjustment */ #define PIPEX_PPP_INGRESS_FILTER 0x0200 /* do ingress filter */ int8_t pr_ccp_id; /* ccp current packet id */ int pr_ppp_id; /* ppp id. */ uint16_t pr_peer_mru; /* peer's mru */ uint16_t pr_timeout_sec; /* idle timer */ struct in_addr pr_ip_srcaddr; /* local IP address */ struct in_addr pr_ip_address; /* framed IP address */ struct in_addr pr_ip_netmask; /* framed IP netmask */ struct sockaddr_in6 pr_ip6_address; /* framed IPv6 address */ int pr_ip6_prefixlen; /* framed IPv6 prefix length */ union { struct { uint32_t snd_nxt; /* send next */ uint32_t rcv_nxt; /* receive next */ uint32_t snd_una; /* unacked */ uint32_t rcv_acked; /* recv acked */ int winsz; /* window size */ int maxwinsz; /* max window size */ int peer_maxwinsz; /* peer's max window size */ } pptp; struct { /* select protocol options: 1 for enable */ uint32_t option_flags; #define PIPEX_L2TP_USE_SEQUENCING 0x00000001 /* use sequence number on L2TP data messages */ uint16_t tunnel_id; /* our tunnel-id */ uint16_t peer_tunnel_id; /* peer's tunnel-id */ uint32_t ns_nxt; /* send next */ uint32_t nr_nxt; /* receive next */ uint32_t ns_una; /* unacked */ uint32_t nr_acked; /* recv acked */ uint32_t ipsecflowinfo; /* IPsec flow id for NAT-T */ } l2tp; struct { char over_ifname[IF_NAMESIZE]; /* ethernet ifname */ } pppoe; } pr_proto; struct sockaddr_storage pr_peer_address; /* peer address of tunnel */ struct sockaddr_storage pr_local_address; /* our address of tunnel */ struct pipex_mppe_req pr_mppe_recv; /* mppe key for receive */ struct pipex_mppe_req pr_mppe_send; /* mppe key for send */ }; ``` The *pipex\_mppe\_req* structure that was used by *pr\_mppe\_recv* and *pr\_mppe\_send* has the following definition: ``` struct pipex_mppe_req { int16_t stateless; /* mppe key mode. 1 for stateless */ int16_t keylenbits; /* mppe key length(in bits)*/ u_char master_key[PIPEX_MPPE_KEYLEN]; /* mppe master key */ }; ``` - PIPEXDSESSION *struct pipex\_session\_close\_req \** Delete the specified session from the kernel. Specify the session using a *pipex\_session\_close\_req* structure, which has the following definition: ``` struct pipex_session_close_req { int psr_protocol; /* tunnel protocol */ uint16_t psr_session_id; /* session-id */ struct pipex_statistics psr_stat; /* statistics */ }; ``` The *psr\_protocol* and *psr\_session\_id* fields used to specify the session are mandatory. On successful return, the *psr\_stat* field is filled by the kernel. See PIPEXGSTAT section for a description of the *pipex\_statistics* structure. - PIPEXGSTAT *struct pipex\_session\_stat\_req \** Get statistics for the specified session. Specify the session using a *pipex\_session\_stat\_req* structure, which has the following definition: ``` struct pipex_session_stat_req { int psr_protocol; /* tunnel protocol */ uint16_t psr_session_id; /* session-id */ struct pipex_statistics psr_stat; /* statistics */ }; ``` The *psr\_protocol* and *psr\_session\_id* fields used to specify the session are mandatory. On successful return, the *psr\_stat* field is filled by the kernel. The *pipex\_statistics* structure has the following definition: ``` struct pipex_statistics { uint32_t ipackets; /* packets received from tunnel */ uint32_t ierrors; /* error packets received from tunnel */ uint64_t ibytes; /* number of received bytes from tunnel */ uint32_t opackets; /* packets sent to tunnel */ uint32_t oerrors; /* error packets on sending to tunnel */ uint64_t obytes; /* number of sent bytes to tunnel */ uint32_t idle_time; /* idle time in seconds */ }; ``` - PIPEXGCLOSED *struct pipex\_session\_list\_req \** Get a list of closed sessions. **pipex** reserves closed sessions for 30 seconds for userland programs to get statistical information. On successful return, the *pipex\_session\_list\_req* structure is filled by the kernel. The structure has the following definition. ``` struct pipex_session_list_req { uint8_t plr_flags; #define PIPEX_LISTREQ_MORE 0x01 /* has more session */ int plr_ppp_id_count; /* count of PPP id */ int plr_ppp_id[PIPEX_MAX_LISTREQ]; /* PPP id */ }; ``` - PIPEXSIFDESCR *struct pipex\_session\_descr\_req \** Set the [pppx(4)](/pppx/4.md) interface's description of the session. This command doesn't work on pppac(4) devices. Specify the session and its description using a *pipex\_session\_descr\_req* structure, which has the following definition: ``` struct pipex_session_descr_req { int pdr_protocol; /* tunnel protocol */ uint16_t pdr_session_id; /* session-id */ char pdr_descr[IFDESCRSIZE]; /* description */ }; ``` ## SEE ALSO [ioctl(2)](/ioctl/2.md), pppac(4), [pppx(4)](/pppx/4.md), [npppd(8)](/npppd/8.md), [sysctl(8)](/sysctl/8.md) ## AUTHORS The **pipex** was written by Internet Initiative Japan Inc. ## BUGS [pppx(4)](/pppx/4.md) does not allow sessions with **pr\_timeout\_sec** set to any value other than 0.