From fb5d1c5d7d0b914a90aaeecf406c7092d9d55aeb Mon Sep 17 00:00:00 2001 From: David Gibson Date: Wed, 19 Oct 2022 11:43:51 +1100 Subject: tap: Remove unhelpeful vnet_pre optimization from tap_send() Callers of tap_send() can optionally use a small optimization by adding extra space for the 4 byte length header used on the qemu socket interface. tap_ip_send() is currently the only user of this, but this is used only for "slow path" ICMP and DHCP packets, so there's not a lot of value to the optimization. Worse, having the two paths here complicates the interface and makes future cleanups difficult, so just remove it. I have some plans to bring back the optimization in a more general way in future, but for now it's just in the way. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- tap.c | 29 +++++++++-------------------- 1 file changed, 9 insertions(+), 20 deletions(-) (limited to 'tap.c') diff --git a/tap.c b/tap.c index 844ee43..07592dd 100644 --- a/tap.c +++ b/tap.c @@ -66,34 +66,24 @@ static PACKET_POOL_NOINIT(pool_tap6, TAP_MSGS, pkt_buf); * @c: Execution context * @data: Packet buffer * @len: Total L2 packet length - * @vnet_pre: Buffer has four-byte headroom * * Return: return code from send() or write() */ -int tap_send(const struct ctx *c, const void *data, size_t len, int vnet_pre) +int tap_send(const struct ctx *c, const void *data, size_t len) { - if (vnet_pre) - pcap((char *)data + 4, len); - else - pcap(data, len); + pcap(data, len); if (c->mode == MODE_PASST) { int flags = MSG_NOSIGNAL | MSG_DONTWAIT; + uint32_t vnet_len = htonl(len); - if (vnet_pre) { - *((uint32_t *)data) = htonl(len); - len += 4; - } else { - uint32_t vnet_len = htonl(len); - - if (send(c->fd_tap, &vnet_len, 4, flags) < 0) - return -1; - } + if (send(c->fd_tap, &vnet_len, 4, flags) < 0) + return -1; return send(c->fd_tap, data, len, flags); } - return write(c->fd_tap, (char *)data + (vnet_pre ? 4 : 0), len); + return write(c->fd_tap, (char *)data, len); } /** @@ -135,10 +125,9 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto, const char *in, size_t len, uint32_t flow) { char buf[USHRT_MAX]; - char *pkt = buf + 4; struct ethhdr *eh; - eh = (struct ethhdr *)pkt; + eh = (struct ethhdr *)buf; /* TODO: ARP table lookup */ memcpy(eh->h_dest, c->mac_guest, ETH_ALEN); @@ -174,7 +163,7 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto, csum_icmp4(ih, ih + 1, len - sizeof(*ih)); } - if (tap_send(c, buf, len + sizeof(*iph) + sizeof(*eh), 1) < 0) + if (tap_send(c, buf, len + sizeof(*iph) + sizeof(*eh)) < 0) debug("tap: failed to send %lu bytes (IPv4)", len); } else { struct ipv6hdr *ip6h = (struct ipv6hdr *)(eh + 1); @@ -215,7 +204,7 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto, ip6h->flow_lbl[2] = (flow >> 0) & 0xff; } - if (tap_send(c, buf, len + sizeof(*ip6h) + sizeof(*eh), 1) < 1) + if (tap_send(c, buf, len + sizeof(*ip6h) + sizeof(*eh)) < 1) debug("tap: failed to send %lu bytes (IPv6)", len); } } -- cgit v1.2.3