On Wed, Apr 02, 2025 at 07:23:26PM +0200, Laurent Vivier wrote:Don't use the memory of the incoming packet to build the outgoing buffer as it can be memory of the TX queue in the case of vhost-user. Moreover with vhost-user, the packet can be splitted accross several iovec and it's easier to rebuild it in a buffer than updating an existing iovec array. Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>Reviewed-by: David Gibson <david(a)gibson.dropbear.id.au>--- arp.c | 84 ++++++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 55 insertions(+), 29 deletions(-) diff --git a/arp.c b/arp.c index fc482bbd9938..9d68d7c3b602 100644 --- a/arp.c +++ b/arp.c @@ -31,56 +31,82 @@ #include "tap.h" /** - * arp() - Check if this is a supported ARP message, reply as needed + * ignore_arp() - Check if this is a supported ARP message * @c: Execution context - * @p: Packet pool, single packet with Ethernet buffer + * @ah: ARP header + * @am: ARP message * - * Return: 1 if handled, -1 on failure + * Return: true if the message is supported, false otherwise. */ -int arp(const struct ctx *c, const struct pool *p) +static bool ignore_arp(const struct ctx *c, + const struct arphdr *ah, const struct arpmsg *am) { - unsigned char swap[4]; - struct ethhdr *eh; - struct arphdr *ah; - struct arpmsg *am; - size_t l2len; - - eh = packet_get(p, 0, 0, sizeof(*eh), NULL); - ah = packet_get(p, 0, sizeof(*eh), sizeof(*ah), NULL); - am = packet_get(p, 0, sizeof(*eh) + sizeof(*ah), sizeof(*am), NULL); - - if (!eh || !ah || !am) - return -1; - if (ah->ar_hrd != htons(ARPHRD_ETHER) || ah->ar_pro != htons(ETH_P_IP) || ah->ar_hln != ETH_ALEN || ah->ar_pln != 4 || ah->ar_op != htons(ARPOP_REQUEST)) - return 1; + return true; /* Discard announcements, but not 0.0.0.0 "probes" */ if (memcmp(am->sip, &in4addr_any, sizeof(am->sip)) && !memcmp(am->sip, am->tip, sizeof(am->sip))) - return 1; + return true; /* Don't resolve the guest's assigned address, either. */ if (!memcmp(am->tip, &c->ip4.addr, sizeof(am->tip))) + return true; + + return false; +} + +/** + * arp() - Check if this is a supported ARP message, reply as needed + * @c: Execution context + * @p: Packet pool, single packet with Ethernet buffer + * + * Return: 1 if handled, -1 on failure + */ +int arp(const struct ctx *c, const struct pool *p) +{ + struct { + struct ethhdr eh; + struct arphdr ah; + struct arpmsg am; + } __attribute__((__packed__)) resp; + const struct ethhdr *eh; + const struct arphdr *ah; + const struct arpmsg *am; + + eh = packet_get(p, 0, 0, sizeof(*eh), NULL); + ah = packet_get(p, 0, sizeof(*eh), sizeof(*ah), NULL); + am = packet_get(p, 0, sizeof(*eh) + sizeof(*ah), sizeof(*am), NULL); + + if (!eh || !ah || !am) + return -1; + + if (ignore_arp(c, ah, am)) return 1; - ah->ar_op = htons(ARPOP_REPLY); - memcpy(am->tha, am->sha, sizeof(am->tha)); - memcpy(am->sha, c->our_tap_mac, sizeof(am->sha)); + /* ethernet header */ + resp.eh.h_proto = htons(ETH_P_ARP); + memcpy(resp.eh.h_dest, eh->h_source, sizeof(resp.eh.h_dest)); + memcpy(resp.eh.h_source, c->our_tap_mac, sizeof(resp.eh.h_source)); - memcpy(swap, am->tip, sizeof(am->tip)); - memcpy(am->tip, am->sip, sizeof(am->tip)); - memcpy(am->sip, swap, sizeof(am->sip)); + /* ARP header */ + resp.ah.ar_op = htons(ARPOP_REPLY); + resp.ah.ar_hrd = ah->ar_hrd; + resp.ah.ar_pro = ah->ar_pro; + resp.ah.ar_hln = ah->ar_hln; + resp.ah.ar_pln = ah->ar_pln; - l2len = sizeof(*eh) + sizeof(*ah) + sizeof(*am); - memcpy(eh->h_dest, eh->h_source, sizeof(eh->h_dest)); - memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source)); + /* ARP message */ + memcpy(resp.am.sha, c->our_tap_mac, sizeof(resp.am.sha)); + memcpy(resp.am.sip, am->tip, sizeof(resp.am.sip)); + memcpy(resp.am.tha, am->sha, sizeof(resp.am.tha)); + memcpy(resp.am.tip, am->sip, sizeof(resp.am.tip)); - tap_send_single(c, eh, l2len); + tap_send_single(c, &resp, sizeof(resp)); return 1; }-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson