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a469fc393f
...so that we'll retry sending them, instead of more-or-less silently dropping them. This happens quite frequently if our sending buffer on the UNIX domain socket is heavily constrained (for instance, by the 208 KiB default memory limit). It might be argued that dropping frames is part of the expected TCP flow: we don't dequeue those from the socket anyway, so we'll eventually retransmit them. But we don't need the receiver to tell us (by the way of duplicate or missing ACKs) that we couldn't send them: we already know as sendmsg() reports that. This seems to considerably increase throughput stability and throughput itself for TCP connections with default wmem_max values. Unfortunately, the 16 bits left as padding in the frame descriptors we use internally aren't enough to uniquely identify for which connection we should update sequence numbers: create a parallel array of pointers to sequence numbers and L4 lengths, of TCP_FRAMES_MEM size, and go through it after calling sendmsg(). Signed-off-by: Stefano Brivio <sbrivio@redhat.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
87 lines
2.8 KiB
C
87 lines
2.8 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 TAP_H
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#define TAP_H
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/**
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* struct tap_hdr - L2 and tap specific headers
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* @vnet_len: Frame length (for qemu socket transport)
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* @eh: Ethernet header
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*/
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struct tap_hdr {
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uint32_t vnet_len;
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struct ethhdr eh;
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} __attribute__((packed));
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#define TAP_HDR_INIT(proto) { .eh.h_proto = htons_constant(proto) }
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static inline size_t tap_hdr_len_(const struct ctx *c)
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{
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if (c->mode == MODE_PASST)
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return sizeof(struct tap_hdr);
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else
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return sizeof(struct ethhdr);
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}
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/**
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* tap_iov_base() - Find start of tap frame
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* @c: Execution context
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* @taph: Pointer to L2 header buffer
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*
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* Returns: pointer to the start of tap frame - suitable for an
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* iov_base to be passed to tap_send_frames())
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*/
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static inline void *tap_iov_base(const struct ctx *c, struct tap_hdr *taph)
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{
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return (char *)(taph + 1) - tap_hdr_len_(c);
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}
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/**
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* tap_iov_len() - Finalize tap frame and return total length
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* @c: Execution context
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* @taph: Tap header to finalize
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* @plen: L2 payload length (excludes L2 and tap specific headers)
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*
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* Returns: length of the tap frame including L2 and tap specific
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* headers - suitable for an iov_len to be passed to
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* tap_send_frames()
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*/
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static inline size_t tap_iov_len(const struct ctx *c, struct tap_hdr *taph,
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size_t plen)
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{
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if (c->mode == MODE_PASST)
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taph->vnet_len = htonl(plen + sizeof(taph->eh));
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return plen + tap_hdr_len_(c);
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}
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struct in_addr tap_ip4_daddr(const struct ctx *c);
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void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
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struct in_addr dst, in_port_t dport,
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const void *in, size_t len);
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void tap_icmp4_send(const struct ctx *c, struct in_addr src, struct in_addr dst,
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const void *in, size_t len);
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const struct in6_addr *tap_ip6_daddr(const struct ctx *c,
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const struct in6_addr *src);
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void tap_udp6_send(const struct ctx *c,
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const struct in6_addr *src, in_port_t sport,
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const struct in6_addr *dst, in_port_t dport,
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uint32_t flow, const void *in, size_t len);
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void tap_icmp6_send(const struct ctx *c,
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const struct in6_addr *src, const struct in6_addr *dst,
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const void *in, size_t len);
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int tap_send(const struct ctx *c, const void *data, size_t len);
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size_t tap_send_frames(const struct ctx *c, const struct iovec *iov, size_t n);
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void tap_update_mac(struct tap_hdr *taph,
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const unsigned char *eth_d, const unsigned char *eth_s);
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void tap_listen_handler(struct ctx *c, uint32_t events);
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void tap_handler_pasta(struct ctx *c, uint32_t events,
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const struct timespec *now);
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void tap_handler_passt(struct ctx *c, uint32_t events,
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const struct timespec *now);
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void tap_sock_init(struct ctx *c);
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#endif /* TAP_H */
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