From ac9811f810114150a8dba66e91b6e48e518a423b Mon Sep 17 00:00:00 2001 From: Darrell Ball Date: Tue, 15 Jan 2019 18:58:17 -0800 Subject: [PATCH] conntrack: Fix FTP seq_skew boundary adjustments. At the same time, splice out a function and also rely on the compiler for overflow/underflow handling. Found by inspection. Fixes: bd5e81a0e596 ("Userspace Datapath: Add ALG infra and FTP.") Signed-off-by: Darrell Ball Signed-off-by: Ben Pfaff --- lib/conntrack.c | 38 ++++++++++---------------------------- 1 file changed, 10 insertions(+), 28 deletions(-) diff --git a/lib/conntrack.c b/lib/conntrack.c index 835afff7859..4a3c2ec1ea9 100644 --- a/lib/conntrack.c +++ b/lib/conntrack.c @@ -3173,6 +3173,13 @@ repl_ftp_v6_addr(struct dp_packet *pkt, struct ct_addr v6_addr_rep, return overall_delta; } +/* Increment/decrement a TCP sequence number. */ +static void +adj_seqnum(ovs_16aligned_be32 *val, int32_t inc) +{ + put_16aligned_be32(val, htonl(ntohl(get_16aligned_be32(val)) + inc)); +} + static void handle_ftp_ctl(struct conntrack *ct, const struct conn_lookup_ctx *ctx, struct dp_packet *pkt, const struct conn *ec, long long now, @@ -3247,34 +3254,9 @@ handle_ftp_ctl(struct conntrack *ct, const struct conn_lookup_ctx *ctx, struct tcp_header *th = dp_packet_l4(pkt); if (nat && ec->seq_skew != 0) { - if (ctx->reply != ec->seq_skew_dir) { - - uint32_t tcp_ack = ntohl(get_16aligned_be32(&th->tcp_ack)); - - if ((ec->seq_skew > 0) && (tcp_ack < ec->seq_skew)) { - /* Should not be possible; will be marked invalid. */ - tcp_ack = 0; - } else if ((ec->seq_skew < 0) && - (UINT32_MAX - tcp_ack < -ec->seq_skew)) { - tcp_ack = (-ec->seq_skew) - (UINT32_MAX - tcp_ack); - } else { - tcp_ack -= ec->seq_skew; - } - ovs_be32 new_tcp_ack = htonl(tcp_ack); - put_16aligned_be32(&th->tcp_ack, new_tcp_ack); - } else { - uint32_t tcp_seq = ntohl(get_16aligned_be32(&th->tcp_seq)); - if ((ec->seq_skew > 0) && (UINT32_MAX - tcp_seq < ec->seq_skew)) { - tcp_seq = ec->seq_skew - (UINT32_MAX - tcp_seq); - } else if ((ec->seq_skew < 0) && (tcp_seq < -ec->seq_skew)) { - /* Should not be possible; will be marked invalid. */ - tcp_seq = 0; - } else { - tcp_seq += ec->seq_skew; - } - ovs_be32 new_tcp_seq = htonl(tcp_seq); - put_16aligned_be32(&th->tcp_seq, new_tcp_seq); - } + ctx->reply != ec->seq_skew_dir ? + adj_seqnum(&th->tcp_ack, -ec->seq_skew) : + adj_seqnum(&th->tcp_seq, ec->seq_skew); } th->tcp_csum = 0;