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tap: Split tap specific and L2 (ethernet) headers

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In some places (well, actually only UDP now) we use struct tap_hdr to
represent both tap backend specific and L2 ethernet headers.  Handling
these together seemed like a good idea at the time, but Laurent's changes
in the TCP code working towards vhost-user support suggest that treating
them separately is more useful, more often.

Alter struct tap_hdr to represent only the TAP backend specific headers.
Updated related helpers and the UDP code to match.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2024-05-01 16:53:45 +10:00 committed by Stefano Brivio
parent c27ca91564
commit 34fb381b5a
2 changed files with 23 additions and 21 deletions
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21
tap.h
View file

@ -6,30 +6,28 @@
#ifndef TAP_H #ifndef TAP_H
#define TAP_H #define TAP_H
#define ETH_HDR_INIT(proto) { .h_proto = htons_constant(proto) }
/** /**
* struct tap_hdr - L2 and tap specific headers * struct tap_hdr - tap backend specific headers
* @vnet_len: Frame length (for qemu socket transport) * @vnet_len: Frame length (for qemu socket transport)
* @eh: Ethernet header
*/ */
struct tap_hdr { struct tap_hdr {
uint32_t vnet_len; uint32_t vnet_len;
struct ethhdr eh;
} __attribute__((packed)); } __attribute__((packed));
#define TAP_HDR_INIT(proto) { .eh.h_proto = htons_constant(proto) }
static inline size_t tap_hdr_len_(const struct ctx *c) static inline size_t tap_hdr_len_(const struct ctx *c)
{ {
if (c->mode == MODE_PASST) if (c->mode == MODE_PASST)
return sizeof(struct tap_hdr); return sizeof(struct tap_hdr);
else else
return sizeof(struct ethhdr); return 0;
} }
/** /**
* tap_frame_base() - Find start of tap frame * tap_frame_base() - Find start of tap frame
* @c: Execution context * @c: Execution context
* @taph: Pointer to L2 and tap specific header buffer * @taph: Pointer to tap specific header buffer
* *
* Returns: pointer to the start of tap frame - suitable for an * Returns: pointer to the start of tap frame - suitable for an
* iov_base to be passed to tap_send_frames()) * iov_base to be passed to tap_send_frames())
@ -43,17 +41,16 @@ static inline void *tap_frame_base(const struct ctx *c, struct tap_hdr *taph)
* tap_frame_len() - Finalize tap frame and return total length * tap_frame_len() - Finalize tap frame and return total length
* @c: Execution context * @c: Execution context
* @taph: Tap header to finalize * @taph: Tap header to finalize
* @plen: L3 packet length (excludes L2 and tap specific headers) * @plen: L2 packet length (includes L2, excludes tap specific headers)
* *
* Returns: length of the tap frame including L2 and tap specific * Returns: length of the tap frame including tap specific headers - suitable
* headers - suitable for an iov_len to be passed to * for an iov_len to be passed to tap_send_frames()
* tap_send_frames()
*/ */
static inline size_t tap_frame_len(const struct ctx *c, struct tap_hdr *taph, static inline size_t tap_frame_len(const struct ctx *c, struct tap_hdr *taph,
size_t plen) size_t plen)
{ {
if (c->mode == MODE_PASST) if (c->mode == MODE_PASST)
taph->vnet_len = htonl(plen + sizeof(taph->eh)); taph->vnet_len = htonl(plen);
return plen + tap_hdr_len_(c); return plen + tap_hdr_len_(c);
} }

23
udp.c
View file

@ -173,7 +173,8 @@ static uint8_t udp_act[IP_VERSIONS][UDP_ACT_TYPE_MAX][DIV_ROUND_UP(NUM_PORTS, 8)
/** /**
* udp4_l2_buf_t - Pre-cooked IPv4 packet buffers for tap connections * udp4_l2_buf_t - Pre-cooked IPv4 packet buffers for tap connections
* @s_in: Source socket address, filled in by recvmmsg() * @s_in: Source socket address, filled in by recvmmsg()
* @taph: Tap-level headers (partially pre-filled) * @taph: Tap backend specific header
* @eh: Prefilled ethernet header
* @iph: Pre-filled IP header (except for tot_len and saddr) * @iph: Pre-filled IP header (except for tot_len and saddr)
* @uh: Headroom for UDP header * @uh: Headroom for UDP header
* @data: Storage for UDP payload * @data: Storage for UDP payload
@ -182,6 +183,7 @@ static struct udp4_l2_buf_t {
struct sockaddr_in s_in; struct sockaddr_in s_in;
struct tap_hdr taph; struct tap_hdr taph;
struct ethhdr eh;
struct iphdr iph; struct iphdr iph;
struct udphdr uh; struct udphdr uh;
uint8_t data[USHRT_MAX - uint8_t data[USHRT_MAX -
@ -192,7 +194,8 @@ udp4_l2_buf[UDP_MAX_FRAMES];
/** /**
* udp6_l2_buf_t - Pre-cooked IPv6 packet buffers for tap connections * udp6_l2_buf_t - Pre-cooked IPv6 packet buffers for tap connections
* @s_in6: Source socket address, filled in by recvmmsg() * @s_in6: Source socket address, filled in by recvmmsg()
* @taph: Tap-level headers (partially pre-filled) * @taph: Tap backend specific header
* @eh: Pre-filled ethernet header
* @ip6h: Pre-filled IP header (except for payload_len and addresses) * @ip6h: Pre-filled IP header (except for payload_len and addresses)
* @uh: Headroom for UDP header * @uh: Headroom for UDP header
* @data: Storage for UDP payload * @data: Storage for UDP payload
@ -202,10 +205,11 @@ struct udp6_l2_buf_t {
#ifdef __AVX2__ #ifdef __AVX2__
/* Align ip6h to 32-byte boundary. */ /* Align ip6h to 32-byte boundary. */
uint8_t pad[64 - (sizeof(struct sockaddr_in6) + sizeof(struct ethhdr) + uint8_t pad[64 - (sizeof(struct sockaddr_in6) + sizeof(struct ethhdr) +
sizeof(uint32_t))]; sizeof(struct tap_hdr))];
#endif #endif
struct tap_hdr taph; struct tap_hdr taph;
struct ethhdr eh;
struct ipv6hdr ip6h; struct ipv6hdr ip6h;
struct udphdr uh; struct udphdr uh;
uint8_t data[USHRT_MAX - uint8_t data[USHRT_MAX -
@ -289,8 +293,8 @@ void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s)
struct udp4_l2_buf_t *b4 = &udp4_l2_buf[i]; struct udp4_l2_buf_t *b4 = &udp4_l2_buf[i];
struct udp6_l2_buf_t *b6 = &udp6_l2_buf[i]; struct udp6_l2_buf_t *b6 = &udp6_l2_buf[i];
eth_update_mac(&b4->taph.eh, eth_d, eth_s); eth_update_mac(&b4->eh, eth_d, eth_s);
eth_update_mac(&b6->taph.eh, eth_d, eth_s); eth_update_mac(&b6->eh, eth_d, eth_s);
} }
} }
@ -307,7 +311,7 @@ static void udp_sock4_iov_init_one(const struct ctx *c, size_t i)
struct iovec *tiov = &udp4_l2_iov_tap[i]; struct iovec *tiov = &udp4_l2_iov_tap[i];
*buf = (struct udp4_l2_buf_t) { *buf = (struct udp4_l2_buf_t) {
.taph = TAP_HDR_INIT(ETH_P_IP), .eh = ETH_HDR_INIT(ETH_P_IP),
.iph = L2_BUF_IP4_INIT(IPPROTO_UDP) .iph = L2_BUF_IP4_INIT(IPPROTO_UDP)
}; };
@ -335,7 +339,7 @@ static void udp_sock6_iov_init_one(const struct ctx *c, size_t i)
struct iovec *tiov = &udp6_l2_iov_tap[i]; struct iovec *tiov = &udp6_l2_iov_tap[i];
*buf = (struct udp6_l2_buf_t) { *buf = (struct udp6_l2_buf_t) {
.taph = TAP_HDR_INIT(ETH_P_IPV6), .eh = ETH_HDR_INIT(ETH_P_IPV6),
.ip6h = L2_BUF_IP6_INIT(IPPROTO_UDP) .ip6h = L2_BUF_IP6_INIT(IPPROTO_UDP)
}; };
@ -608,7 +612,7 @@ static size_t udp_update_hdr4(const struct ctx *c, struct udp4_l2_buf_t *b,
b->uh.dest = htons(dstport); b->uh.dest = htons(dstport);
b->uh.len = htons(datalen + sizeof(b->uh)); b->uh.len = htons(datalen + sizeof(b->uh));
return tap_frame_len(c, &b->taph, ip_len); return tap_frame_len(c, &b->taph, ip_len + sizeof(b->eh));
} }
/** /**
@ -676,7 +680,8 @@ static size_t udp_update_hdr6(const struct ctx *c, struct udp6_l2_buf_t *b,
b->uh.len = b->ip6h.payload_len; b->uh.len = b->ip6h.payload_len;
csum_udp6(&b->uh, src, dst, b->data, datalen); csum_udp6(&b->uh, src, dst, b->data, datalen);
return tap_frame_len(c, &b->taph, payload_len + sizeof(b->ip6h)); return tap_frame_len(c, &b->taph, payload_len +
sizeof(b->ip6h) + sizeof(b->eh));
} }
/** /**