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| author | Stefano Brivio <sbrivio@redhat.com> | 2021-10-15 17:09:37 +0200 |
|---|---|---|
| committer | Stefano Brivio <sbrivio@redhat.com> | 2021-10-15 17:09:37 +0200 |
| commit | 54e6513d17802200538e30d54845b18abbe2ec0f (patch) | |
| tree | 415b2e7e0b166c20462148222357c504e73f1e5b /tcp.c | |
| parent | bf63832207f0e13e5bda564d2be993f10b0fb458 (diff) | |
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tcp: Clamp MSS depending on IP version, properly derive buffer sizes
It makes no sense to include an IPv6 header in the calculation for
clamping MSS on IPv4.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Diffstat (limited to 'tcp.c')
| -rw-r--r-- | tcp.c | 36 |
1 files changed, 19 insertions, 17 deletions
@@ -352,6 +352,11 @@ #define MAX_WS 10 #define MAX_WINDOW (1 << (16 + (MAX_WS))) #define MSS_DEFAULT 536 +#define MSS4 (USHRT_MAX - sizeof(uint32_t) - sizeof(struct ethhdr) - \ + sizeof(struct iphdr) - sizeof(struct tcphdr)) +#define MSS6 (USHRT_MAX - sizeof(uint32_t) - sizeof(struct ethhdr) - \ + sizeof(struct ipv6hdr) - sizeof(struct tcphdr)) + #define WINDOW_DEFAULT 14600 /* RFC 6928 */ #define SYN_TIMEOUT 240000 /* ms */ @@ -590,7 +595,8 @@ static struct tcp4_l2_buf_t { struct ethhdr eh; /* 30 14 */ struct iphdr iph; /* 44 28 */ struct tcphdr th; /* 64 48 */ - uint8_t data[USHRT_MAX - sizeof(struct tcphdr)]; + uint8_t data[MSS4]; /* 84 68 */ + /* 65541 65525 */ #ifdef __AVX2__ } __attribute__ ((packed, aligned(32))) #else @@ -622,8 +628,8 @@ struct tcp6_l2_buf_t { struct ethhdr eh; /* 18 6 */ struct ipv6hdr ip6h; /* 32 20 */ struct tcphdr th; /* 72 60 */ - uint8_t data[USHRT_MAX - - (sizeof(struct ipv6hdr) + sizeof(struct tcphdr))]; + uint8_t data[MSS6]; /* 92 80 */ + /* 65639 65627 */ #ifdef __AVX2__ } __attribute__ ((packed, aligned(32))) #else @@ -1868,14 +1874,12 @@ static void tcp_conn_from_tap(struct ctx *c, int af, void *addr, if (conn->mss_guest < 0) conn->mss_guest = MSS_DEFAULT; + /* Don't upset qemu */ if (c->mode == MODE_PASST) { - /* Don't upset qemu */ - conn->mss_guest = MIN(USHRT_MAX - - sizeof(uint32_t) - - sizeof(struct ethhdr) - - sizeof(struct ipv6hdr) - - sizeof(struct tcphdr), - conn->mss_guest); + if (af == AF_INET) + conn->mss_guest = MIN(MSS4, conn->mss_guest); + else + conn->mss_guest = MIN(MSS6, conn->mss_guest); } sl = sizeof(conn->mss_guest); @@ -2563,14 +2567,12 @@ int tcp_tap_handler(struct ctx *c, int af, void *addr, if (conn->mss_guest < 0) conn->mss_guest = MSS_DEFAULT; + /* Don't upset qemu */ if (c->mode == MODE_PASST) { - /* Don't upset qemu */ - conn->mss_guest = MIN(USHRT_MAX - - sizeof(uint32_t) - - sizeof(struct ethhdr) - - sizeof(struct ipv6hdr) - - sizeof(struct tcphdr), - conn->mss_guest); + if (af == AF_INET) + conn->mss_guest = MIN(MSS4, conn->mss_guest); + else + conn->mss_guest = MIN(MSS6, conn->mss_guest); } /* info.tcpi_bytes_acked already includes one byte for SYN, but |