AGW(LVS)后端RS全挂代码优化

来源：互联网发布：c语言大于等于符号编辑：程序博客网时间：2024/05/23 14:38

转载请注明出处：http://blog.csdn.net/hliyuxin/article/details/43375327

如果LVS上一个VIP下挂的RS全都不可用，原LVS采用的方式是DROP掉访问该VIP的包。出现这种情况，我们需要最短时间反馈给监控该VIP不可用，降低应用的不可用时长。我们采用的改进方法是当该VIP的RS都不可用时，第一个syn包直接回复RST包，这个结果类似访问一个IP不存在的PORT。

设计方法是svc结构体增加weight变量，代表下挂rs的weight的和，当rs都不可用时svc->weight = 0.处理逻辑：

RST包构造代码（DPDK）

unsigned short tmpport;
uint32_t tmpAddr;

struct ipv4_hdr *iph = ipv4_hdr(mbuf);
struct tcp_hdr *th = tcp_v4_hdr(iph);
uint32_t tcphoff = ipv4_hdrlen(iph);

int needs_ack = 0;
uint32_t tcplen = rte_cpu_to_be_16(iph->total_length) - tcphoff;

/* reset seq ack_seq */
if(unlikely(th->tcp_flags & TCP_FLAG_ACK)) {
th->sent_seq = th->recv_ack;
th->recv_ack = 0;
} else {
needs_ack = 1;
th->recv_ack = htonl(ntohl(th->sent_seq) + 1 /* 1 means: th->syn + th->fin */
+ tcplen - (th->data_off>>2)); /* oldskb seq+len */
th->sent_seq = 0;
}

/* Set rst-ack flag */
th->tcp_flags = TCP_FLAG_RST ;
if(likely(needs_ack))
th->tcp_flags |= TCP_FLAG_ACK;

th->data_off = sizeof(struct tcp_hdr) << 2;
th->rx_win = 0;
th->tcp_urp = 0;

/* Exchange ports */
tmpport = th->dst_port;
th->dst_port = th->src_port;
th->src_port = tmpport;

/* Exchange ip addr */
tmpAddr = iph->src_addr;
iph->src_addr = iph->dst_addr;
iph->dst_addr = tmpAddr;

iph->version_ihl = 0x45;
iph->type_of_service = 0;
iph->packet_id = 0x1314;
iph->total_length = rte_cpu_to_be_16(sizeof(struct ipv4_hdr) + sizeof(struct tcp_hdr));
iph->fragment_offset = rte_cpu_to_be_16(IP_DF);
iph->next_proto_id = IPPROTO_TCP;
iph->time_to_live = 128;
iph->type_of_service = 0;
iph->hdr_checksum = 0;

mbuf->ol_flags |= PKT_TX_IP_CKSUM;
mbuf->ol_flags &= ~PKT_TX_TCP_CKSUM;
th->cksum = 0;
th->cksum = get_ipv4_udptcp_checksum(iph,(uint16_t*)th);

mbuf->pkt.vlan_macip.f.l2_len = sizeof(struct ether_hdr);
mbuf->pkt.vlan_macip.f.l3_len = sizeof(struct ipv4_hdr);

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