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When available, we want to retrieve our socket peer's advertised window and forward that to the guest. That information has been available from the kernel via the TCP_INFO getsockopt() since kernel commit 8f7baad7f035. Currently our probing for this is a bit odd. The HAS_SND_WND define determines if our headers include the tcp_snd_wnd field, but that doesn't necessarily mean the running kernel supports it. Currently we start by assuming it's _not_ available, but mark it as available if we ever see a non-zero value in the field. This is a bit hit and miss in two ways: * Zero is perfectly possible window the peer could report, so we can get false negatives * We're reading TCP_INFO into a local variable, which might not be zero initialised, so if the kernel _doesn't_ write it it could have non-zero garbage, giving us false positives. We can use a more direct way of probing for this: getsockopt() reports the length of the information retreived. So, check whether that's long enough to include the field. This lets us probe the availability of the field once and for all during initialisation. That in turn allows ctx to become a const pointer to tcp_prepare_flags() which cascades through many other functions. We also move the flag for the probe result from the ctx structure to a global, to match peek_offset_cap. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
72 lines
2.0 KiB
C
72 lines
2.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later
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* Copyright (c) 2021 Red Hat GmbH
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* Author: Stefano Brivio <sbrivio@redhat.com>
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*/
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#ifndef TCP_H
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#define TCP_H
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#define TCP_TIMER_INTERVAL 1000 /* ms */
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struct ctx;
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void tcp_timer_handler(const struct ctx *c, union epoll_ref ref);
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void tcp_listen_handler(const struct ctx *c, union epoll_ref ref,
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const struct timespec *now);
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void tcp_sock_handler(const struct ctx *c, union epoll_ref ref,
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uint32_t events);
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int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af,
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const void *saddr, const void *daddr,
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const struct pool *p, int idx, const struct timespec *now);
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int tcp_sock_init(const struct ctx *c, sa_family_t af, const void *addr,
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const char *ifname, in_port_t port);
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int tcp_init(struct ctx *c);
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void tcp_timer(struct ctx *c, const struct timespec *now);
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void tcp_defer_handler(struct ctx *c);
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void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s);
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int tcp_set_peek_offset(int s, int offset);
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extern bool peek_offset_cap;
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/**
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* union tcp_epoll_ref - epoll reference portion for TCP connections
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* @index: Index of connection in table
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* @u32: Opaque u32 value of reference
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*/
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union tcp_epoll_ref {
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uint32_t index:20;
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uint32_t u32;
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};
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/**
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* union tcp_listen_epoll_ref - epoll reference portion for TCP listening
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* @port: Bound port number of the socket
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* @pif: pif in which the socket is listening
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* @u32: Opaque u32 value of reference
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*/
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union tcp_listen_epoll_ref {
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struct {
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in_port_t port;
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uint8_t pif;
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};
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uint32_t u32;
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};
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/**
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* struct tcp_ctx - Execution context for TCP routines
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* @port_to_tap: Ports bound host-side, packets to tap or spliced
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* @fwd_in: Port forwarding configuration for inbound packets
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* @fwd_out: Port forwarding configuration for outbound packets
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* @timer_run: Timestamp of most recent timer run
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* @pipe_size: Size of pipes for spliced connections
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*/
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struct tcp_ctx {
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struct fwd_ports fwd_in;
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struct fwd_ports fwd_out;
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struct timespec timer_run;
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size_t pipe_size;
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};
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#endif /* TCP_H */
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